description of the cerebral vasculature in a …

DESCRIPTION OF THE CEREBRAL VASCULATURE IN A SOUTHERN

AFRICAN CADAVER COHORT

by

Karen Cilliers

Thesis presented in partial fulfilment of the requirments for the degree

Master of Science in Anatomy at

Stellenbosch University

Supervisor: Prof Benedict John Page

Faculty of Medicine and Health Sciences

March 2016

ii

DECLARATION

By submitting this thesis electronically, I declare that the entirety of the work contained therein is my

own, original work, that I am the sole author thereof (save to the extent explicitly otherwise stated), that

reproduction and publication thereof by Stellenbosch University will not infringe any third party rights

and that I have not previously in its entirety or in part submitted it for obtaining any qualification.

March 2016

Copyright © 2016 Stellenbosch University

All rights reserved

Stellenbosch University https://scholar.sun.ac.za

iii

ABSTRACT

Few studies give a complete description on the origin, absence, duplication and triplication of the

cerebral cortical branches. The anterior cerebral artery (ACA) varies considerably and this complicates

the description of the normal anatomy. The most commonly discussed branching types of the middle

cerebral artery (MCA) include bifurcation and trifurcation. Branching of the posterior cerebral artery

(PCA) has not been adequately described; only the division level of the parieto-occipital (PoA) and

calcarine arteries has been discussed. Anomalies of the cerebral arteries have been reported. To the

author’s best knowledge, no previous studies have investigated the anatomy of the cerebral arteries in a

Western Cape population. Therefore, the aim of this study is to describe the anatomy and anomalies of

the cerebral vasculature in a Southern African cadaver cohort.

Twenty hemispheres were used for the pilot study and 126 hemispheres for the present study.

These 126 hemispheres consisted of 88 males and 38 females, between the ages of 22 and 84. Specimens

were distributed over three population groups, namely, coloured (n=76), black (n=38), white (n=10) and

unknown (n=2). The arteries were injected with coloured silicone. The external diameter and length of

all the cortical branches of the cerebral arteries were measured using a digital micrometre.

The diameter and lengths indicated statistically significant differences on the right and left side,

between males and females, different population groups and different age groups. The most commonly

absent artery was the callosomarginal artery, and the most commonly duplicated artery was the

paracentral lobule artery. The origin of the cortical branches was similar to the descriptions in the

literature; however, the common trunks and unusual origins were also noted. The branching pattern of

the MCA was classified according to the 11 different subtypes described in the literature. Medial

bifurcation was most commonly observed. The branching pattern of the PCA was assessed, and in most

cases there was additional branching before the division of the calcarine artery and PoA. Anomalies

observed in the present study included bihemispheric ACA (19.8%), median ACA (11.6%) and

fenestration of the PCA (1.6%). The only anomaly observed in the pilot study was fenestration of the

PCA (5.0%).

A shorter trunk may play a role in aneurysm formation, and changes in vessel diameter could

indicate early signs of several pathological conditions. Aneurysms can be observed at the branching of

cerebral vessels, highlighting the importance of a thorough knowledge of the vascular anatomy. The

MCA branching subtypes were described, since only bifurcation and trifurcation are usually noted.

Furthermore, the branching pattern of the PCA has not been adequately described in previous reports;


iv

therefore the possible branching types were defined. Anomalies of the cerebral arteries are usually only

mentioned; therefore the bihemispheric and median ACA were fully described (origin, length, diameter

and area supplied). Given the important implications that the anatomical variation of the cerebral arteries

may have, future research should focus on giving a more comprehensive description of the anatomy.


v

OPSOMMING

Min studies bied 'n volledige beskrywing van die oorsprong, afwesigheid, duplisering en triplisering van

die serebrale kortikale arteries. Die verloop van die anterior serebrale arterie (ASA) varieer aansienlik

wat beskrywing van die normale anatomie bemoeilik. Die mees algemeenste vertakkingstipes van die

middel serebrale arterie (MSA) sluit bifurkasie en trifurkasie in. Vertakking van die posterior serebrale

arterie (PSA) word nie voldoende beskryf nie; slegs die vlak van die oorsprong van die parieto-oksipitaal

(PoA) en kalkariene arteries word bespreek. Variasies in die anatomie van die serebrale arteries kan

waargeneem word. Sover die kennis van die outeur strek, is geen studies oor die anatomie van die

serebrale arteries voorheen op 'n Wes-Kaapse populasiegroep voltooi nie. Die doel van hierdie studie is

om die kortikale arteries in 'n Suid-Afrikaanse kadawer populasie te beskryf.

Twintig hemisfere is vir die loodsstudie en 126 hemisfere vir die huidige studie gebruik. Die 126

hemisfere het bestaan uit 88 mans en 38 vrouens, tussen die ouderdom van 22 en 84 jaar. Die

studiepopulasie het bestaan uit drie populasie groepe; kleurling (n=76), swart (n=38), wit (n=10) en

onbekende (n=2) groepe. Die arteries is met gekleurde silikoon ingespuit. Die eksterne deursnit en lengte

van al die kortikale arteries is met 'n digitale mikrometer gemeet.

Die deursnit en lengtes het statisties beduidende verskille tussen links en regs, mans en vrouens,

verskillende populasiegroepe en verskillende ouderdomsgroepe getoon. Die kallosomarginale arterie

was oor die algemeen die meeste afwesig, en die parasentrale lobule arterie was die mees algemeenste

arterie wat verdubbeld is. Alhoewel gemeenskaplike stamme en ongewone oorspronge ook opgemerk

is, is die oorspronge van die kortikale arteries soortgelyk aan beskrywings wat in die literatuur voorkom.

Die vertakkingspatroon van die MSA is volgens die 11 verskillende subtipes wat in die literatuur beskryf

is, geklassifiseer. Mediale bifurkasie is die meeste waargeneem. Die vertakkingspatroon van die PSA is

geëvalueer, en in die meeste gevalle was daar 'n bykomende vertakking voor verdeling van die PoA en

kalkariene arterie. Abnormale variasies wat in die huidige studie waargeneem is sluit ‘n bihemisferiese

ASA (19.8%),’n mediaane ASA (11.6%) en fenestrasie in die PSA (1.6%) in. Die enigste abnormale

variasie wat in die loodsstudie waargeneem is, was fenestrasie in die PSA (5.0%).

‘n Korter arteriële stam kan 'n rol speel in die vorming van aneurismes, en veranderinge in die

deursnit kan vroeë tekens van verskeie patologiese toestande aandui. Aneurismes word dikwels by die

vertakking van serebrale arteries waargeneem, wat die belang van 'n deeglike kennis van die vaskulêre

anatomie beklemtoon. Die vertakking subtipes van die MSA is deeglik beskryf, aangesien slegs

bifurkasie en trifurkasie gewoonlik in die literatuur bespreek word. Die vertakkingspatroon van die PSA


vi

is nie voldoende in vorige studies beskryf nie; dus is al die moontlike vertakkingstipes gedefinieer.

Abnormale variasie van die serebrale arteries word gewoonlik net genoem; dus is die bihemisferiese en

mediaane ASA volledig beskryf (oorsprong, lengte, deursnit en area van voorsiening). Gegewe die

implikasies van anatomiese variasies van die serebrale arteries, behoort toekomstige navorsing te fokus

op 'n meer omvattende beskrywing van die anatomie.


vii

ACKNOWLEDGEMENTS

Firstly I would like to thank God for His presence in my life. I would also like to thank my supervisor,

Prof BJ Page. Thank you to the University of Stellenbosch and the Division of Anatomy and Histology

for financial assistance and for the opportunity to attend and present a poster at the 17th International

Conference on Microscopic and Macroscopic Anatomy in Barcelona, Spain. I am grateful for the

opportunity to publish a part of this thesis, in an upcoming issue of Turkish Neurosurgery.

I am thankful for the financial support of the Harry Crossley Foundation, without this financial support

this project would not have been possible. I am also thankful for the financial support during my masters

from Prof NC Gey van Pittius. I am grateful to Mr MT Chirehwa for statistical analysis and I would like

to thank Mrs LM Greyling, Dr E Geldenhuys and Ms PC Kotze for editing.

Thank you to Mr RP Williams, Mr A Marthie and the Honours students for technical assistance with

removal of the brains. A special thanks to Ms J Walters and Mr RP Williams for assistance with

perfusion. I am grateful for the continuous support of the Masters students and for the support of family

and friends.


viii

CONTENTS

DECLARATION ..................................................................................................................................... ii

ABSTRACT ........................................................................................................................................... iii

OPSOMMING .......................................................................................................................................... v

ACKNOWLEDGEMENTS ................................................................................................................... vii

TABLES ................................................................................................................................................ xii

FIGURES ............................................................................................................................................... xiv

ABBREVIATIONS ............................................................................................................................... xvi

CHAPTER ONE: INTRODUCTION……………………………...…………………………………Error! Bookmar k not define d.1

CHAPTER TWO: LITERATURE REVIEW ........................................................................................... 4

2.1. ANTERIOR CEREBRAL ARTERY ........................................................................................ 5

2.1.1. Segmentation ...................................................................................................................... 5

2.1.2. Cortical branches ................................................................................................................ 6

2.1.2.1. Callosomarginal artery ................................................................................................ 7

2.1.2.2. Infra-orbital and frontopolar artery ............................................................................. 7

2.1.2.3. Internal frontal arteries ................................................................................................ 7

2.1.2.4. Paracentral lobule artery and internal parietal arteries .............................................. 11

2.1.3. Anomalies ......................................................................................................................... 14

2.1.3.1. Azygos anterior cerebral artery ................................................................................. 15

2.1.3.2. Bihemispheric anterior cerebral artery ...................................................................... 16

2.1.3.3. Median anterior cerebral artery ................................................................................. 16

2.1.3.4. Supreme anterior communicating artery ................................................................... 17

2.1.3.5. Fenestration ............................................................................................................... 17

2.2. MIDDLE CEREBRAL ARTERY ........................................................................................... 20

2.2.1. Segmentation .................................................................................................................... 20

2.2.2. Branching pattern .............................................................................................................. 21

2.2.3. Early branching ................................................................................................................. 23

2.2.4. Cortical branches .............................................................................................................. 23

2.2.4.1. Origins ....................................................................................................................... 24

2.2.4.2. Early branches ........................................................................................................... 24

2.2.5. Anomalies ......................................................................................................................... 25


ix

2.2.5.1. Duplicated middle cerebral artery ............................................................................. 26

2.2.5.2. Accessory middle cerebral artery .............................................................................. 27

2.2.5.3. Fenestration ............................................................................................................... 28

2.3. POSTERIOR CEREBRAL ARTERY ..................................................................................... 31

2.3.1. Segments ........................................................................................................................... 31

2.3.2. Cortical arteries ................................................................................................................. 32

2.3.2.1. Temporal arteries ....................................................................................................... 32

2.3.2.2. Splenial artery ............................................................................................................ 34

2.3.2.3. Terminal trunks ......................................................................................................... 35

2.3.2.4. Diameter and Lengths ............................................................................................... 37

2.3.3. Branching pattern .............................................................................................................. 37

2.3.4. Anomalies ......................................................................................................................... 38

2.3.4.1. Fenestration ............................................................................................................... 38

2.3.4.2. Duplicated and triplicated posterior cerebral arteries ................................................ 39

CHAPTER THREE: PROBLEM STATEMENT, AIM, OBJECTIVES ............................................... 40

3.1. PROBLEM STATEMENT ...................................................................................................... 41

3.2. AIM .......................................................................................................................................... 41

3.3. OBJECTIVES .......................................................................................................................... 41

CHAPTER FOUR: MATERIALS AND METHODS ........................................................................... 42

4.1. STUDY POPULATION .......................................................................................................... 43

4.2. REMOVAL OF THE BRAIN ................................................................................................. 44

4.3. PREPARATION OF THE SPECIMENS ................................................................................ 44

4.4. MEASUREMENT OF THE VESSELS .................................................................................. 46

4.5. STATISTICAL ANALYSIS ................................................................................................... 46

CHAPTER FIVE: RESULTS ................................................................................................................. 48

5.1. PILOT STUDY: ANTERIOR CEREBRAL ARTERY .......................................................... 49

5.2. PILOT STUDY: MIDDLE CEREBRAL ARTERY ............................................................... 52

5.3. PILOT STUDY: POSTERIOR CEREBRAL ARTERY ......................................................... 55

5.4. PRESENT STUDY: ANTERIOR CEREBRAL ARTERY .................................................... 59

5.4.1. Segments ........................................................................................................................... 59

5.4.2. Cortical Branches .............................................................................................................. 61

5.4.2.1. Diameter and Length ................................................................................................. 61


x

5.4.2.2. Absence, duplication and triplication ........................................................................ 63

5.4.2.3. Origins ....................................................................................................................... 63

5.4.3. Anomalies ......................................................................................................................... 67

5.4.3.1. Median anterior cerebral artery ................................................................................. 67

5.4.3.2. Bihemispheric anterior cerebral artery ...................................................................... 69

5.5. PRESENT STUDY: MIDDLE CEREBRAL ARTERY ......................................................... 77

5.5.1. Trunks ............................................................................................................................... 77


5.5.2.1. Diameter and length .................................................................................................. 79


5.5.2.3. Origins ....................................................................................................................... 81

5.5.2.4. Early branches ........................................................................................................... 85

5.5.3. Branching .......................................................................................................................... 85

5.5.4. Anomalies ......................................................................................................................... 90

5.2. PRESENT STUDY: POSTERIOR CEREBRAL ARTERY ................................................... 91

5.2.1. Segments ........................................................................................................................... 91


5.2.2.1. Diameter and Length ................................................................................................. 93


5.2.2.3. Origins ....................................................................................................................... 95

5.2.3. Branching ........................................................................................................................ 100

5.2.4. Anomalies ....................................................................................................................... 103

CHAPTER SIX: DISCUSSION ........................................................................................................... 105

6.1. ANTERIOR CEREBRAL ARTERY .................................................................................... 106

6.1.1. Diameter and length ........................................................................................................ 106

6.1.2. Presence, duplication, and triplication ............................................................................ 107

6.1.3. Origins ............................................................................................................................ 108

6.1.4. Anomalies ....................................................................................................................... 110

6.2. MIDDLE CEREBRAL ARTERY ......................................................................................... 112


6.2.2. Predivision length ........................................................................................................... 113

6.2.3. Absence, duplication, triplication ................................................................................... 114


xi

6.2.4. Origins ............................................................................................................................ 114

6.2.5. Early branches ................................................................................................................ 115

6.2.6. Branching ........................................................................................................................ 115

6.2.7. Anomalies ....................................................................................................................... 116

6.3. POSTERIOR CEREBRAL ARTERY ................................................................................... 119


6.3.2. Absence, duplication, triplication ................................................................................... 119

6.3.3. Origins ............................................................................................................................ 120

6.3.4. Branching ........................................................................................................................ 121

6.3.5. Anomalies ....................................................................................................................... 121

6.4. LIMITATIONS ...................................................................................................................... 123

CHAPTER SEVEN: CONCLUSION .................................................................................................. 124

REFERENCES ..................................................................................................................................... 128


xii

TABLES

Table 2.1: The presence and origins of the infra-orbital, frontopolar and callosomarginal arteries ........ 9

Table 2.2: The presence and origins of the anterior, middle and posterior internal frontal arteries ....... 10

Table 2.3: The presence and origins of the paracentral lobule artery and internal parietal arteries ....... 12

Table 2.4: The average diameter (mm) and length (mm) of the anterior cerebral cortical branches ..... 13

Table 2.5: The prevalence of the azygos, bihemispheric, and median anterior cerebral arteries ........... 19

Table 2.6: The prevalence of monofurcation, bifurcation, trifurcation and tetrafurcation ..................... 23

Table 2.7: The prevalence of fenestration, duplicated and accessory middle cerebral arteries .............. 29

Table 2.8: Origins of the temporal and common temporal arteries ........................................................ 33

Table 2.9: The prevalence of the temporal artery configurations ........................................................... 34

Table 2.10: Origins of the splenial, parieto-occipital and calcarine arteries .......................................... 36

Table 2.11: The average diameter (mm) and length (mm) of the posterior cerebral artery segments. .. 37

Table 2.12: The prevalence of the posterior cerebral artery anomalies .................................................. 38

Table 4.1: Study population information. ............................................................................................... 44

Table 5.1: The average diameter (mm), average length (mm), presence, duplication, triplication and

origins of the anterior cerebral cortical branches observed in the pilot study. ....................................... 50


origins of the middle cerebral cortical branches observed in the pilot study. ........................................ 53


origins of the posterior cerebral cortical branches observed in the pilot study. ..................................... 56

Table 5.4: The average diameter (mm) and length (mm) of the A2, A3 and A4 segments observed

bilaterally, between males and females, different population groups and different age groups. ........... 60

Table 5.5: The average diameter (mm) and length (mm) of the anterior cerebral cortical branches

observed bilaterally, between males and females, different population groups and different age

groups ..................................................................................................................................................... 62

Table 5.6: The presence, duplication, triplication and origin of the anterior cerebral cortical branches

observed in the present study. ................................................................................................................. 64

Table 5.7: The diameter (mm), length (mm) and cortical arteries originating from the bihemispheric

and median anterior cerebral artery. ....................................................................................................... 74


xiii

Table 5.8: The average diameter (mm) of the M1 segment, superior, middle and inferior trunks


groups ..................................................................................................................................................... 78

Table 5.9: The diameter (mm) of the M1 segment and predivision length (mm) .................................. 78

Table 5.10: The average diameter (mm) and length (mm) of the middle cerebral cortical branches


groups. .................................................................................................................................................... 80

Table 5.11: The presence, duplication, triplication and origin of the middle cerebral cortical branches


Table 5.12: Configuration of the superior temporal arteries. ................................................................. 84

Table 5.13: The prevalence of the MCA branching observed bilaterally, between males and females,

different population groups and in different age groups. ....................................................................... 87

Table 5.14: The average diameter (mm) and length (mm) of the P2A, P2P and P3 segments observed

bilaterally, between males and females, different population groups and different age groups. ........... 92

Table 5.15: The average diameter (mm) and length (mm) of the posterior cerebral cortical branches


groups. .................................................................................................................................................... 94

Table 5.16: The presence, duplication, triplication and origin of the posterior cerebral cortical branches


Table 5.17: Configuration of the inferior temporal arteries. .................................................................. 98

Table 5.18: The branching subtypes of the posterior cerebral artery. .................................................. 100


xiv

FIGURES

Figure 2.1: The different configurations of the anterior cerebral artery. .................................................. 6

Figure 2.2: The different anomalous patterns of the anterior cerebral artery ......................................... 14

Figure 2.3: The five different types of the azygos anterior cerebral artery ............................................ 16

Figure 2.4: Anterior cerebral artery fenestrations. .................................................................................. 18

Figure 2.5: The different segments of the middle cerebral artery .......................................................... 20

Figure 2.6: The 11 different branching patterns of the middle cerebral artery. ...................................... 22

Figure 2.7: Illustration of the most common origins of the cortical branches originating from the

superior, inferior and middle trunk ......................................................................................................... 24

Figure 2.8: Anomalies of the middle cerebral artery .............................................................................. 26

Figure 2.9: The different segments and cortical branches of the posterior cerebral artery. ................... 31

Figure 2.10: Anomalies of the posterior cerebral artery ......................................................................... 39

Figure 4.1: Perfusion of the cerebral arteries. ......................................................................................... 45

Figure 5.1: The inferior internal parietal artery originating from the posterior cerebral artery. ............ 51

Figure 5.2: Fenestration of the P2A segment. ........................................................................................ 57

Figure 5.3: The different branching types of the posterior cerebral artery ............................................. 58

Figure 5.4: The most common origins of the anterior cerebral cortical branches. ................................. 63

Figure 5.5: The different configurations of the callosomarginal artery.................................................. 66

Figure 5.6: The different configurations of the internal frontal artery. .................................................. 66

Figure 5.7: The median anterior cerebral arteries observed in the present study. .................................. 68

Figure 5.8: Median anterior cerebral artery. ........................................................................................... 69

Figure 5.9: Bihemispheric anterior cerebral arteries observed in the present study. .............................. 70

Figure 5.10: Bihemispheric anterior cerebral artery ............................................................................... 72

Figure 5.11: The measurements of the anomalies of the anterior cerebral artery. ................................. 73

Figure 5.12: Clarification on the median anterior cerebral artery, the bihemispheric anterior cerebral

artery, and unusual origin of a cortical artery. ........................................................................................ 75

Figure 5.13: The most common origins of the middle cerebral cortical branches. ................................ 81

Figure 5.14: Configuration of the superior temporal arteries. ................................................................ 85

Figure 5.15: The six cases of true trifurcation of the middle cerebral artery. ........................................ 86

Figure 5.16: The middle cerebral artery branching subtypes ................................................................. 89

Figure 5.17: Triplicated anterior inferior temporal artery ...................................................................... 95


xv

Figure 5.18: Configuration of the inferior temporal arteries. ................................................................. 99

Figure 5.19: Early branching of the posterior cerebral artery .............................................................. 101

Figure 5.20: The branching patterns of the posterior cerebral artery ................................................... 102

Figure 5.21: Fenestration of the right (A) and left (B) posterior cerebral artery .................................. 103


xvi

ABBREVIATIONS

AA Angular artery

ACA Anterior cerebral artery

AChA Anterior choroidal artery

AcoA Anterior communicating artery

AIFA Anterior internal frontal artery (Anteromedial frontal branch)

AITA Anterior inferior temporal artery

APA Anterior parietal artery

ATA Anterior temporal artery

BihemACA Bihemispheric anterior cerebral artery

CA Central artery

CmA Callosomarginal artery

EFB Early frontal branch

ETB Early temporal branch

FpA Frontopolar artery (Polar frontal artery)

IFA Internal frontal artery

IfO Infra-orbital artery (Medial orbitofrontal artery)

IIPA Inferior internal parietal artery

MCA Middle cerebral artery

MedACA Median anterior cerebral artery

MIFA Middle internal frontal artery (Intermediomedial frontal branch)

MITA Middle inferior temporal artery

MTA Middle temporal artery

OfA Orbitofrontal artery (Lateral orbitofrontal artery)

PCA Posterior cerebral artery

PcA Precentral artery

PfA Prefrontal artery

PIFA Posterior internal frontal artery (Posteromedial frontal branch)

PITA Posterior inferior temporal artery

PLA Paracentral lobule artery

PoA Parieto-occipital artery


xvii

PPA Posterior parietal artery

PrcA Pericallosal artery

PTA Posterior temporal artery

RaH Recurrent artery of Heubner

SA Splenial artery

SIPA Superior internal parietal artery

ToA Temporo-occipital artery

TpA Temporopolar artery (Polar temporal artery)


1

CHAPTER ONE

INTRODUCTION

LITERATURE


2

The cerebral cortex is primarily supplied by the anterior, middle and posterior cerebral arteries. The

anterior cerebral artery (ACA) and posterior cerebral artery (PCA) mainly supply the medial and

posterior surface of the cerebral hemisphere, while the middle cerebral artery (MCA) supplies the lateral

surface of the cerebral hemisphere1.

The segmentation of the ACA is mostly agreed on by different authors, although the relationship of the

pericallosal (PrcA) and callosomarginal arteries (CmA) is not agreed upon. The ACA varies considerably

and this complicates the description of the normal anatomy2. The ACA may have a more simplistic

structure compared to the MCA, although more variations are observed in the ACA compared to the

MCA2-6. The branches of the MCA cover a large part of the lateral surface of each hemisphere; therefore

it is likely to be exposed during surgical intervention in this area7, 8. Segments of the MCA are similarly

described by most authors; however, there is still some disagreement on the branching pattern of the

MCA5. The posterior circulation is complex, tends to vary and very few studies have focussed on the

anatomy of the PCA9. It is important to be aware of the possibility of variations, since these variations

can have serious clinical implications. The knowledge of these variations can be helpful to clinicians and

neurosurgeons10.

The literature review gives an extensive summary of the cerebral segments and cortical branches. The

different branching types and the cerebral anomalies were discussed. An extensive report on the

prevalence of the cerebral anomalies was given. An illustration of the different MCA subtypes was

provided since there is still confusion on these subtypes.

In the present study, a detailed analysis was done on the diameter and length of the cerebral segments

and cortical branches to indicate possible statistically significant differences on the left and right side,

between age, population groups, and sex. To the author’s best knowledge, this has been poorly reported

in previous studies. The pilot and present study also reported on the origins, absence, duplication and

triplication of the cortical branches, since few studies have focussed on these aspects. The anatomy of

the temporal superior and temporal inferior arteries have been scarcely documented, thus a detailed

description was given on the anatomy of these arteries. Possible common trunks are also not thoroughly

reported in the literature. These aspects were reported on in the pilot and present study. The criteria for

each MCA branching subtype has not been previously described, thus this was noted in the pilot study.

The prevalence of these branching subtypes was noted in the pilot and present study.


3

The PCA is the most neglected cerebral artery; therefore special attention was given on the anatomy of

the PCA. A revised classification of the inferior temporal arteries, which excludes the hippocampal

arteries, and takes into account the origins of the inferior temporal cortical branches of the PCA, was

suggested. The branching pattern of the PCA has not been adequately described; therefore the branching

pattern was re-evaluated and described as monofurcation, bifurcation and trifurcation.

More information was given on the origin, diameter, length and area supplied by the ACA anomalies

and additional criteria were given to classify the ACA anomalies. To the author’s best knowledge, this

is the first study on the anatomy of the cerebral vasculature to be completed on a Western Cape

population or in South Africa.


4

CHAPTER TWO

LITERATURE REVIEW

1 LITERATURE REVIEW


5

2.1. ANTERIOR CEREBRAL ARTERY

The anatomy of the anterior cerebral artery (ACA) varies considerably which complicates the description

of the ACA and its branches. The segmentation of the ACA is described similarly by various authors11-

14, however, the relationship of the pericallosal (PrcA) and callosomarginal arteries (CmA) is not agreed

upon2.

2.1.1. Segmentation

Different terms and definitions are often used to describe the ACA segments3, 11, 15. The ACA can be

divided into proximal and distal segments, or pre- and post-communicating segments. The ACA can also

be described in three separate parts, namely the A1 segment (also referred to as the horizontal proximal

or pre-communicating segment), the A2 segment (the vertical proximal or post-communicating

segment), and the A3 segment (the distal parts and cortical branches)13.

Most studies8, 12-16, however, refer to the A1, A2, A3, A4 and A5 segments. The A1 segment runs from

the origin of the ACA to the level of the AcoA. The pericallosal artery arises distal to the A1 segment

and consists of several segments that can be divided according to their relationship with the corpus

callosum. The A2 segment (also referred to as the infracallosal section) runs vertically from the anterior

communicating artery (AcoA) to the genu of the corpus callosum. The A3 segment (also referred to as

the precallosal part) curves around the genu, and the A4 segment (also referred to as the supracallosal

section) usually runs in the sulcus of the corpus callosum and almost reaches the splenium8, 12-14. The A5

segment (cortical branches) varies considerably; it is therefore difficult to describe a standard arterial

pattern for this segment2. The two basic configurations of the ACA are determined by the presence or

absence of the CmA12, 15, 16. The different configurations and segments of the ACA are illustrated in

Figure 2.1.


6

Figure 1.1: The different configurations of the anterior cerebral artery. A) Callosomarginal

artery is absent; and B) Callosomarginal artery is present. (AcoA) Anterior communicating artery;

(AIFA) Anterior internal frontal artery; (CmA) Callosomarginal artery; (FpA) Frontopolar artery; (IfO)

Infra-orbital artery; (IIPA) Inferior internal parietal artery; (MIFA) Middle internal frontal artery;

(PLA) Paracentral lobule artery; (PIFA) Posterior internal frontal artery; (PrcA) Pericallosal artery; and

(SIPA) Superior internal parietal artery.

The A2 and A3 segments have collectively been referred to as the ascending or vertical segment and the

A4 and A5 segments as the horizontal segment14, 15. The ACA have also been divided into a basal and a

distal part. The basal part runs from the origin to the rostrum of the corpus callosum, and the distal part

runs around the genu and superior to the corpus callosum14.

Several authors refer to the A1 segment as the anterior cerebral artery and the artery distal to the AcoA

as the pericallosal artery3, 11, 14-16. The A1 and A2 segments have also been referred to as the anterior

cerebral artery and the artery distal to the origin of the callosomarginal artery, the pericallosal artery14.

Since the origin of the CmA can vary, this terminology can be problematic11. Furthermore, the CmA is

not always present, therefore it is preferable to classify the pericallosal artery as the part distal to the

AcoA8, 14, 17.

2.1.2. Cortical branches

The ACA cortical branches include the infra-orbital artery (IfO), frontopolar artery (FpA), anterior

internal frontal artery (AIFA), middle internal frontal artery (MIFA), posterior internal frontal artery

(PIFA), callosomarginal artery (CmA), paracentral lobule artery (PLA), superior internal parietal artery


7

(SIPA) and inferior internal parietal artery (IIPA). These branches can originate from the A2, A3, A4

and A5 segments as single branches or as common trunks.

2.1.2.1. Callosomarginal artery

The CmA can be seen as the largest branch of the pericallosal artery16. The CmA has been defined as

the artery that runs in or near the cingulate sulcus and gives off two or more cortical branches. This

definition is problematic since there can occasionally be more than one artery that arise from the

pericallosal artery, run in the cingulate sulcus and give rise to a number of cortical branches2.

In a study by Ugur et al.2 a new classification system was proposed; the CmA was either defined as

typical, atypical or absent. An atypical CmA was observed when there was only a very short artery

coursing in the cingulate sulcus and two symmetrical callosomarginal arteries can also be present in the

same hemisphere2. A typical CmA has a longer course compared to an atypical callosomarginal artery

and usually originates from the A3 segment2, 14, 17, 18. The callosomarginal artery can originate from the

A2 segment, A3 or A4 segment8, 19. Ugur et al.2 observed typical, atypical and absent CmAs in 49.0%,

34.0% and 17.0% of cases respectively. The callosomarginal artery has been observed in 40.0% to 93.4%

of specimens (Table 2.1)2, 3, 14-18, 20-26. The variability regarding the absence or presence of the CmA can

be ascribed to the different definitions that are used for this artery25.

2.1.2.2. Infra-orbital and frontopolar artery

The infra-orbital artery (IfO) normally originates from either the A2 segment, the callosomarginal artery

or as a common trunk with the frontopolar artery3, 11, 27, 28. In rare cases the IfO can originate from the

A1 segment or from the internal frontal arteries. The infra-orbital artery was present in 3.6% to 100% of

cases in a number of studies (Table 2.1)2, 3, 14-16, 21, 22. Duplication of the IfO was observed in 6.0% (three

cases)15, 39.4% (15 cases)3 and 42.0% (21 cases)2 in the literature. Ugur et al.2 observed three and four

infra-orbital arteries in 16.0% and 4.0%, respectively. The frontopolar artery (FpA) usually arises from

the A2 segment or callosomarginal artery2, 3, 11, 27. The FpA was present in 12.5% to 100% of cases in

several studies (Table 2.1)2, 3, 14, 16, 21, 22.

2.1.2.3. Internal frontal arteries

The anterior, middle and posterior internal frontal arteries usually arise separately, although the internal

frontal branches can occasionally originate from a common trunk, referred to as the internal frontal artery


8

(IFA)2. Ugur et al.2 found that the internal frontal artery was present in 58.0% (29 cases) of the study

population. A number of studies2, 3, 14, 16, 17, 21, 22 observed the anterior internal frontal artery (AIFA) in

33.9% to 100% of cases, the middle internal frontal artery (MIFA) in 64.3% to 100% of cases and the

posterior internal frontal artery (PIFA) in 67.9% to 100% of cases (Table 2.2).


9

Table 1.1: The presence and origins of the infra-orbital, frontopolar and callosomarginal arteries2, 14, 16, 17, 21, 22, 29, 30.

Total Presence A1 A2 A3 A4 CmA Special

IfO Perlmutter & Rhoton (1978) 50 100% - 82.5% - - - CT FpA: 18.0%

Gomes et al. (1986) 30 100% - 100% - - - -

Kakou et al. (2000) 46 100% 17.0% 83.0% - - - -

Avci et al. (2003) 62 100% - 100% - - - -

Ugur et al. (2006) 50 100% 1.0% 64.0% - - - -

Kedia et al. (2013) 15 100% 16.3% 83.3% - - - -

FpA Perlmutter & Rhoton (1978) 50 100% - 90.0% - 10.0% - -

Gomes et al. (1986) 30 100% - 100% - - - -

Kakou et al. (2000) 46 100% 17.0% 65.0% 9.0% 9.0% - -

Avci et al. (2003) 62 100% - 95.0% 5.0% - - -

Ugur et al. (2006) 50 98.0% - 72.0% - 9.0% - IFA: 14.0%,

AIFA: 3.0%

Kedia et al. (2013) 15 100% - 40.0% 56.6% 3.3% - -

CmA Perlmutter & Rhoton (1978) 50 82.0% - 12.2% 73.2% - 14.6% -

Gomes et al. (1986) 30 91.6% - 3.6% 90.9% - 5.4% -

Kawashima et al. (2003) 22 91.0% - 4.5% 91.0% - AcoA: 4.5%

Ugur et al. (2006) 50 83.0% - 18.0% 64.0% - 12.0% AcoA: 6.0%

Cavalcanti et al. (2010) 60 93.3% - 10.3% 55.2% - 24.1% AcoA: 10.3%

Kedia et al. (2013) 15 93.4% - 10.0% 50.0% - 40.0% -

(AcoA) Anterior communicating artery; (CmA) Callosomarginal artery; (CT) Common trunk; (FpA) Frontopolar artery; (IFA) Internal

frontal artery; and (IfO) Infra-orbital artery.


10

Table 1.2: The presence and origins of the anterior, middle and posterior internal frontal arteries2, 14, 17, 21, 22.

Total Presence A2 A3 CmA IFA A4 Special

AIFA Perlmutter & Rhoton (1978) 50 86.0% 16.3% 55.8% 27.9% - - -

Gomes et al. (1986) 30 96.6% - 6.8% 84.4% - 8.6% -

Kakou et al. (2000) 46 100% - 65.0% 35.0% - - -

Ugur et al. (2006) 50 100% 4.0% 10.0% 18.0% 53.0% - FpA:15.0%

Kedia et al. (2013) 15 100% 13.3% 60.0% 26.6% - - -

MIFA Perlmutter & Rhoton (1978) 50 90.0% 2.2% 46.7% 46.7% - 4.4% -

Gomes et al. (1986) 30 98.3% - 3.3% 77.9% - 16.9% A5: 1.6%

Ugur et al. (2006) 50 100% - 21.0% 25.0% 50.0% - FpA: 4.0%

Kedia et al. (2013) 15 100% - 43.3% 43.3% - 13.4% -

PIFA Perlmutter & Rhoton (1978) 50 76.0% - 31.6% 36.8% - 31.6% -

Gomes et al. (1986) 30 91.6% - - 56.3% - 36.3% A5: 7.2%

Ugur et al. (2006) 50 100% - 12.0% 48.0% 32.0% 2.0% PLA: 6.0%

Kedia et al. (2013) 15 100% - 10.0% 80.0% - 10.0% -

(AIFA) Anterior internal frontal artery; (CmA) Callosomarginal artery; (FpA) Frontopolar artery; (IFA) Internal frontal artery; (MIFA)

Middle internal frontal artery; (PIFA) Posterior internal frontal artery; and (PLA) Paracentral lobule artery.


11

2.1.2.4. Paracentral lobule artery and internal parietal arteries

The paracentral lobule artery (PLA) can be viewed as the vessel with the most regular origin, course and

area supplied, and was present in 53.6% to 100% of cases studied in the literature (Table 2.3)2, 3, 14, 16, 21,

22.

The superior internal parietal artery (SIPA) normally originates from the A4 segment and runs to the

precuneus11. Ugur et al.2 found that the SIPA can also arise from the callosomarginal artery or the

paracentral lobule artery. The inferior internal parietal artery (IIPA) originates from the A5 segment and

runs to the lower third of the precuneus11. Numerous studies2, 3, 14, 17, 21, 22 observed the SIPA in 78.0% to

100% of cases and the IIPA in 60.0% to 85.0% of cases (Table 2.3).

The diameter and length of the cortical branches of the ACA have been measured previously in the

literature and this is depicted in Table 2.4. According to the literature2, 3, 14, 16, 21, 22, the CmA is generally

the largest cortical ACA branch, and the infra-orbital and IIPA are the smallest cortical branches.


12

Table 1.3: The presence and origins of the paracentral lobule artery and internal parietal arteries2, 14, 17, 21, 22.

Total Presence A3 CmA A4 A5 Special

PLA Perlmutter & Rhoton (1978) 50 90.0% 20.0% 28.9% 35.6% 15.6% -

Gomes et al. (1986) 30 98.3% - 16.9% 33.8% 49.1% -

Kakou et al. (2000) 46 - 50.0% 50.0% - - -

Ugur et al. (2006) 50 100% 12.0% 66.0% 20.0% - IFA: 2.0%

Kedia et al. (2013) 15 100% - 93.4% 6.6% - -

SIPA Perlmutter & Rhoton (1978) 50 78.0% - 23.1% 12.8% 64.1% -

Gomes et al. (1986) 30 85.0% - - - 100% -

Kakou et al. (2000) 46 100% - 15.0% 35.0% 50.0% -

Ugur et al. (2006) 50 88.0% 3.0% 30.0% 33.0% 24.0% PLA: 10.0%

Kedia et al. (2013) 15 93.0% - - 80.0% 20.0% -

IIPA Perlmutter & Rhoton (1978) 50 64.0% - 3.1% 16.6% 81.3% -

Gomes et al. (1986) 30 60.0% - - - 100% -

Kakou et al. (2000) 46 67.0% - - - 100% -

Ugur et al. (2006) 50 85.0% - - 10.0% 75.0% SIPA: 15.0%

Kedia et al. (2013) 15 60.0% - - - 100% -

(CmA) Callosomarginal artery; (IFA) Internal frontal artery; (IIPA) Inferior internal parietal artery; (PLA) Paracentral lobule artery; and

(SIPA) Superior internal parietal artery.


13

Table 1.4: The average diameter (mm) and length (mm) of the anterior cerebral cortical branches2, 3, 14, 16, 21, 22, 29.

Diameter IfO FpA CmA IFA AIFA MIFA PIFA PLA SIPA IIPA

Perlmutter & Rhoton (1978) 0.9 1.3 1.8 - 1.3 1.3 1.4 1.3 1.2 1.1

Gomes et al. (1986) 0.9 1.2 1.8 - 1.0 1.0 1.0 1.1 0.8 0.7

Stefani et al. (2000) 0.9 1.1 1.8 - 1.3 1.4 1.3 1.2 1.0 0.8

Ugur et al. (2006) 1.1 1.4 1.9 1.7 1.3 1.2 1.3 1.4 1.3 1.2

Cavalcanti et al. (2010) 0.6 0.9 1.5 - 1.1 1.1 1.0 1.0 1.1 -

Kedia et al. (2013) 0.2 0.5 1.1 - 0.4 0.4 0.3 0.3 0.3 0.2

Length IfO FpA CmA IFA AIFA MIFA PIFA PLA SIPA IIPA

Perlmutter & Rhoton (1978) 5.0 14.0 43.0 - 47.0 65.0 73.0 79.0 92.0 131.0

Stefani et al. (2000) 7.7 21.6 29.4 - 41.3 56.8 70.3 84.8 101.6 112.6

Avci et al. (2003) 6.0 14.6 - - - - - - - -

(AIFA) Anterior internal frontal artery; (CmA) Callosomarginal artery; (FpA) Frontopolar artery; (IFA) Internal frontal artery; (IfO) Infra-

orbital artery; (IIPA) Inferior internal parietal artery; (MIFA) Middle internal frontal artery; (PIFA) Posterior internal frontal artery; (PLA)

Paracentral lobule artery; and (SIPA) Superior internal parietal artery.


14

2.1.3. Anomalies

The anomalies of the distal ACA have been divided into three major groups (Fig. 2.2). These anomalies

include an azygos ACA, bihemispheric ACA (BihemACA) and a median anterior cerebral artery

(MedACA). Other variations include fenestrations, complete absence of a pericallosal artery and four

pericallosal vessels31, 32. Duplication of the ACA bilaterally (four pericallosal vessels) was observed by

Jain33 in 0.3% (two cases) and Ozaki et al.32 in 0.7% (one case). Ladziński et al.34 observed an additional

ACA branch that originated from the ipsilateral internal carotid artery. Burbank and Morris35 observed

a left ACA arising from the right internal carotid artery and noted that only one similar other case was

described in the literature.

Figure 1.2: The different anomalous patterns of the anterior cerebral artery3. A) Normal

pattern; B) Median anterior cerebral artery; C) Azygos anterior cerebral artery; and D)

Bihemispheric anterior cerebral artery. (ACA) Anterior cerebral artery; (AcoA) Anterior

communicating artery; (AIFA) Anterior internal frontal artery; (FpA) Frontopolar artery; (IfO) Infra-

orbital artery; (IIPA) Inferior internal parietal artery; (MIFA) Middle internal frontal artery; (PIFA)

Posterior internal frontal artery; (PLA) Paracentral lobule artery; and (SIPA) Superior internal parietal

artery.


15

Most variations have no clinical relevance, although these anomalies may predispose patients to

aneurysm formation. Occlusion of some of these anomalies can cause cerebral ischemia to both

hemispheres36.

2.1.3.1. Azygos anterior cerebral artery

The azygos ACA (Fig. 2.2) is formed by the fusion of the two A2 segments and runs along the medial

surface of the hemispheres. It usually divides below the genu to supply both hemispheres2, 11, 14, 16, 17, 19,

21-26, 28, 31, 32, 34, 35, 37-46. The azygos ACA can also be formed when the embryonic median artery persists,

along with lack of development of the A2 segments46, 47.

The azygos ACA usually has little clinical significance45, although this variation may be associated with

other anomalies including agenesis of the corpus callosum, formation of arteriovenous malformations

and ischemia10, 48. Some authors state that aneurysms are frequently associated with an azygos ACA37,

39, 49, whereas others state that this association is extremely rare50, 51. Since this artery supplies parts of

both hemispheres, occlusion may result in a large ischemic area39, 45, 52. The azygos ACA was observed

in 0.04% to 10.0% (Table 2.5)2, 3, 10, 19-21, 24, 36, 49, 51, 53-69 of cases studied.

The degree of fusion between the left and right ACA can vary from minor contact to a long single trunk70,

71. Kapoor et al.62 noted that the trunk could be fused for 5.0 mm to 40.0 mm. When the arteries are fused

for a shorter length, the variation can also be termed long fusion (an anterior communicating artery

variation). Vasović72 observed an azygos ACA that was fused for 3.3 mm and then divided into three

arteries, the right and left A2 segments and a median anterior cerebral artery.

Gunnal et al.10 divided the azygos ACA into five subgroups (Fig. 2.3). Type I is the classic or true azygos

ACA while Type II consists of a shorter stem. Two A2 segments are described in Type III, although one

terminates early. In Type IV there are two A2 segments, although one segment terminates as the

callosomarginal artery. Type V is the median anterior cerebral artery10. In 112 specimens, Gunnal et al.10

observed these five types in 2.7%, 1.8%, 3.6%, 2.7% and 0.9% respectively. The azygos ACA should

not be confused with the bihemispheric ACA (classified as Type III and Type IV)52, 68, 73.


16

Figure 1.3: The five different types of the azygos anterior cerebral artery as described by Gunnal

et al.10.

The classic or true azygos anterior cerebral artery (Type 1) can be described as an artery that does not

divide into two separate distal ACAs and gives rise to all cortical branches of both hemispheres.

However, the azygos ACA typically divides close to the genu (Type II) into two pericallosal arteries to

supply both hemispheres10. This variation is more commonly observed compared to the true azygos

ACA42.

2.1.3.2. Bihemispheric anterior cerebral artery

A bihemispheric ACA is classified when one A2 segment is hypoplastic (or terminates early) and the

contralateral artery divides to supply both hemispheres (Fig. 2.2)8, 13-15, 19, 41, 45, 46, 53. A bihemispheric

ACA was present in 0.9% to 64.0% (Table 2.5)14, 15, 19, 20, 22, 25, 26, 36, 54, 61, 74-76 of specimens cited in the

literature. Baptista54 observed a case (0.3%) with a bihemispheric branch and a median anterior cerebral

artery present.

2.1.3.3. Median anterior cerebral artery

When the median ACA is observed, a third distal ACA is present and can branch to the medial surface

of one or both hemispheres (Fig. 2.2)3, 11, 41, 46, 54, 62, 70, 77. The median ACA usually curves around the

genu and ends at the level of the body of the corpus callosum78. The cause is unknown, although this

variation can be the result of the persistent or patent development of the median artery of corpus

callosum, possibly due to a hypoplastic ACA41, 45, 77. A median ACA was present in 0.9% to 33.3%


17

(Table 2.5)3, 19, 21, 22, 25, 26, 32, 33, 36, 49, 53, 54, 57, 59, 62, 64-69, 76, 78-87 of cases by previous authors. The average

diameter of the median ACA was listed as 0.9 mm88 and 1.3 mm78.

The median anterior cerebral artery usually originates from the AcoA8, 40, 42, 45, 67, 77, 79, 89. In the literature

the median ACA originated from the AcoA in 87.0%62, 90.0%78 and 100%17, 22, 25, 32, 33, 69, 80, 88 of cases.

Alternatively, the artery can originate from the junction of the A1 and A2 segments observed in 10.0%78

and 13.0%62 of cases.

2.1.3.4. Supreme anterior communicating artery

When an additional connection between the right and left A2 segments above the AcoA is present, this

can be referred to as the supreme AcoA10, 90. The junction can also be termed the superior anterior

communicating artery91. Laitinen and Snellman90 observed this variation between the two pericallosal

bifurcations. The supreme AcoA was observed in 20.0% (one case)91 and 21.4% (three cases)90 in the

literature.

2.1.3.5. Fenestration

Fenestration occurs when the lumen of an artery is divided into two segments. It can also be referred to

as partial duplication46, 58, 92-94. Both segments have an endothelium and muscular layer although the

adventitia can be shared46. There are two types of fenestrations; small slit-like and large convex-like

fenestrations and the small slit-like fenestration is the most common type95.

These incomplete duplications are usually present in the vertebrobasilar region although it has been

observed in the ACA46, 58, 95-98. The weakness of the wall of the fenestration and hemodynamic stress at

these locations can play a role in aneurysm formation68, thus there may be an association between

aneurysms and fenestrations99.

Fenestrations of the ACA usually occur at the distal part of the A1 segment68, 96, specifically the distal

half or two-thirds of the A1 segment100-102. Few authors specify in which part of the A1 segment the

fenestration was observed. Ito et al.103 stated that in all three cases they observed, the fenestration was

located in the medial half of the A1 segment, while Yamada et al.104 observed a fenestration in the middle

part of the A1 segment. The cause is unknown; however, these fenestrations may be remnants of a

plexiform anastomosis45. Fenestrations of the ACA were observed in the literature in 0.06% to 6.9%


18

(Table 2.5)32, 36, 53, 55, 56, 58, 68, 99, 105-108 of cases previously studied. Figure 2.4 illustrates the different

locations of the ACA fenestration.

Figure 1.4: Anterior cerebral artery fenestrations. A) Anterior communicating artery

fenestration; B) A2 segment fenestration; C) Proximal A1 segment fenestration; D) Middle A1

segment fenestration; and E) Distal A1 segment fenestration.

Very few authors specified whether the fenestrations were small slit-like or large convex-like

fenestrations. Large convex-like fenestrations were observed in 1.0% (nine cases) and smaller slit-like

fenestrations were observed in 0.2% (two cases) by Uchino et al.68. Fenestrations of the ACA on both

sides are extremely rare103, although Friedlander and Oglivy109 and Vucetić110 each reported a case of

bilateral fenestration in the A1 segment.


19

Table 1.5: The prevalence of the azygos, bihemispheric, and median anterior cerebral arteries2, 3,

10, 14, 15, 19-22, 24-26, 32, 33, 36, 49, 51, 53-69, 74-76, 78-87, 99, 105-108.

Total Azygos ACA BihemACA Median ACA Fenestration

Cases % Cases % Cases % Cases %

Windle (1888) 200 6 3.0% - - 9 4.5% - -

Fawcett & Blachford (1905) 700 - - - - 23 3.3% - -

Baptista (1963) 381 1 0.3% 45 11.8% 50 13.1% - -

Jain (1964) 300 - - - - 26 8.7% - -

Fisher (1965) 414 7 1.7% - - - - - -

Lemay & Gooding (1966) 107 4 3.7% - - - - - -

Wollschlaeger et al. (1967) 291 3 1.0% - - - - 14 4.8%

Ring & Waddington (1968) 25 - - 2 8.0% - - - -

Dunker & Harris (1976) 20 2 10.0% - - - - - -

Ozaki et al. (1977) 146 - - - - 21 14.2% 3 2.1%

Perlmutter & Rhoton (1978) 25 - - 16 64.0% - - - -

Tulleken (1978) 75 1 1.3% - - 8 10.7% - -

Huber et al. (1980) 7782 17 0.2% - - - - - -

Kwak et al. (1980) 296 - - - - 13 4.4% - -

Kayembe et al. (1984) 44 - - - - 10 22.7% - -

Gomes et al. (1986) 30 1 3.3% - - 1 3.3% - -

Marinković et al. (1990) 22 - - - - 2 9.1% - -

Ogawa et al. (1990) 206 - - - - 27 13.1% - -

Nathal et al. (1992) 134 % - - 5 3.7% - -

van der Zwan et al. (1992) 25 - - 2 8.0% - - - -

Sanders et al. (1993) 5190 2 0.04% - - - - 3 0.06%

Macchi et al. (1996) 100 2 2.0% - - 9 9.0% - -

Serizawa et al. (1997) 30 1 3.3% - - 2 6.7% - -

Stefani et al. (2000) 38 1 2.6% - - 3 7.9% - -

Avci et al. (2001) 25 1 4.0% - - 1 4.0% - -

Kulenović et al. (2003) 1 - - - - 1 1.0% - -

Paul & Mishra (2004) 50 - - 1 2.0% - - - -

Ugur et al. (2005) 20 1 5.0% 1 5.0% - - - -

Tao et al. (2006) 45 - - - - 1 2.2% - -

Uchino et al. (2006b) 891 18 2.0% - - 27 3.0% 11 1.2%

Ugur et al. (2006) 50 2 4.0% - - - - - -

Bharatha et al. (2008) 504 1 0.2% - - - - 35 6.9%

Kahilogullari et al. (2008) 30 - - - - 10 33.3% - -

Kapoor et al. (2008) 1000 9 0.9% - - 23 2.3% - -

Lehecka et al. (2008) 101 4 4.0% 15 14.9% 4 4.0% - -

Saidi et al. (2008) 72 - - 4 5.6% - - - -

Nowinski et al. (2009) - - 3.7% - - - - - -

Zurada et al. (2010) 115 2 1.7% - - 3 2.6% - -

Bayrak et al. (2011) 396 - - - - - - 21 5.3%

Nordon & Rodrigues (2012) 50 - - - - 3 6.0% - -

Sun et al. (2012) 4652 - - - - - - 8 0.2%

Swetha (2012) 70 - - - - 1 1.4% - -

Cilliers et al. (2013) 39 - - - - 5 12.8% - -

Gunnal et al. (2013) 112 5 4.4% 7 6.3% 1 0.9% - -

Hamidi et al. (2013) 500 9 1.8% 9 1.8% 5 1.0% 12 2.4%

Kedia et al. (2013) 15 - - 1 6.7% 1 6.7% - -

Stefani et al. (2013) 30 - - 2 6.7% 1 3.3% - -

Cooke et al. (2014) 10927 - - - - - - 43 0.4%

Kovač et al. (2014) 455 7 1.5% 4 0.9% 10 2.2% 3 0.7%

Vasović et al. 2014 266 13 4.9%

Wan-Yin et al. (2014) 3572 14 0.4% - - - - - -

van Rooij et al. (2015) 179 - - - - - - 4 2.2%


20

2.2. MIDDLE CEREBRAL ARTERY

The middle cerebral artery (MCA) is the most complex cerebral artery; however, fewer anomalies are

found compared to the other cerebral arteries5, 6, 8, 27, 111-115. The branches of the MCA cover a large part

of the lateral surface of each hemisphere; therefore it is likely to be exposed during surgical intervention

in this area7, 8.

2.2.1. Segmentation

The MCA can be divided into four anatomical segments. These include the M1 segment (also referred

to as the sphenoid or horizontal segment), the M2 or insular segment, the M3 or opercular segment, and

the M4 segment or cortical branches8, 11-13. The different segments are illustrated in Figure 2.5.

Figure 1.5: The different segments of the middle cerebral artery13.

Some authors7, 8, 12, 13 define the M1 segment as the section from the origin of the MCA to the genu

(curve of the MCA), while others refer to the M1 segment as the part from the origin to the main

branching. The M1 segment can be divided into the pre- and post-bifurcation segments (Fig. 2.5)7, 12, 13.

The M2 segment begins when the MCA turns posterosuperiorly from the genu11-13. The M3 segment

begins at the circular sulcus as the M2 segment turns laterally in the Sylvian fissure. The cortical

branches (M4 segment) begin at the Sylvian fissure and extend over the surface of the hemispheres7, 12.


21

2.2.2. Branching pattern

Various authors11-13, 116 describe different branching types of the MCA and 11 different types can be

distinguished from the literature (Fig. 2.6). The two most commonly observed configurations are the

bifurcating and trifurcating patterns13. Tetrafurcation (also referred to as quadrafurcation),

pseudotetrafurcation and a single trunk (monofurcation) have also been observed. When monofurcation

(Fig. 2.6A) is present, a single trunk with no main branching is observed. Grellier et al.116 described

monofurcation as branching after the limen insulae.

The bifurcation branching type can further be divided into medial and lateral bifurcation (Fig. 2.6D and

E), and medial and lateral pseudobifurcation (Fig. 2.6F and G). Medial and lateral branching refers to

the distance of the branching from the MCA origin (branching close or further away, respectively).

Pseudobifurcation (also referred to as false bifurcation) is when an artery originates from the main trunk

(segment before initial branching) and gives a false impression of a bifurcation11.

Grellier et al.116 stated that the length of the main trunk could be divided into three types; short (3-12

mm), medium (13-22 mm) and long (23-40 mm). The short length could refer to early branching,

although most authors117-120 defined early branching as branching within 5 mm from the MCA origin.

The medium and long length is similar to lateral and medial bifurcation described by Krayenbuhl et al.11;

however, the authors did not state the lengths that were used to classify these bifurcation subtypes.

True trifurcation (Fig. 2.6H) is rarely observed, although the trifurcation subtypes (pseudotrifurcation,

proximal trifurcation and distal trifurcation) are more commonly observed. In these subtypes the MCA

bifurcates and the dominant branch subsequently bifurcates again to give rise to the middle branch. With

pseudotrifurcation (Fig. 2.6I), the distance between the first and second bifurcation is less than 2 mm,

and this subtype is observed least. It should be noted that this branching type can be classified as

triplication in certain studies. With proximal trifurcation (Fig. 2.6J), the most common subtype, the

distance between the first and second bifurcation is more than 2 mm. In distal trifurcation (Fig. 2.6K)

the distance between the two bifurcations is more than 2 mm, and more than a quarter of the distance

between the MCA origin and the first bifurcation5.


22

Isolan et al.115 described pseudotetrafurcation (Fig. 2.6C) as bifurcation of both the inferior and superior

trunks near the initial bifurcation. This gives the false impression of a tetrafurcation (Fig. 2.6B) of the

MCA115. The distance between the first and second bifurcation should be less than 2 mm.

Figure 1.6: The 11 different branching patterns of the middle cerebral artery.

A) Monofurcation; B) Tetrafurcation; C) Pseudotetrafurcation; D) Medial bifurcation; E)

Lateral bifurcation; F) Medial pseudobifurcation; G) Lateral pseudobifurcation; H) True

trifurcation; I) Pseudotrifurcation; J) Proximal trifurcation; and K) Distal trifurcation.

Monofurcation was observed in 3.8% to 17.5%113, 116, 119, 121-124 of cases in previous studies. Bifurcation

was observed in 64.3% to 92.7%5-7, 33, 80, 113, 114, 116, 119, 121-128 of cases, and trifurcation was found in 7.0%

to 61.0%5-7, 24, 33, 80, 113, 114, 116, 119, 121-129 of cases. Pseudotrifurcation was present in 3.0% (three cases)129,

15.0% (five cases)5 and 20.0% (two cases)127. Kahilogullari et al.5 observed proximal trifurcation in

55.0% (18 cases) and distal trifurcation in 30.0% (ten cases). Tetrafurcation was observed in 0.7% to

10.0%7, 119, 121, 122, 126 of cases, and pseudotetrafurcation was observed in 3.3% (one case)115 of cases. The

prevalence of the different branching patterns are summarised in Table 2.6; these varied observations

can indicate that different definitions may be used by different authors for the classification of branching.


23

Table 1.6: The prevalence of monofurcation, bifurcation, trifurcation and tetrafurcation6, 7, 24, 33,

80, 113, 114, 116, 119, 121-129.

Monofurcation Bifurcation Trifurcation Tetrafurcation

Total Cases % Cases % Cases % Cases %

Jain (1964) 300 - - 270 90.0% 30 10.0% - -

Grellier et al. (1978) 280 49 17.5% 199 71.1% 32 11.4% - -

Gibo et al. (1981) 50 - - 39 78.0% 6 12.0% 5 10.0%

Umansky et al. (1984) 70 4 5.7% 45 64.3% 20 28.6% 1 1.4%

Atunes (1985) 37 - - 33 89.2% 4 10.8% - -

Umansky et al. (1985) 34 - - 24 70.6% 7 20.6% 3 8.8%

Umansky et al. (1988) 104 4 3.8% 69 66.3% 27 26.0% 4 3.8%

Anderhuber et al. (1990) 100 - - - - 7 7.0% - -

Meneses et al. (1997) 14 1 7.1% 12 85.7% 1 7.1% - -

Idowu et al. (2002) 100 6 6.0% 81 81.0% 13 13.0% - -

Kulenović et al. (2003) - - - - 70.0% - 30.0% - -

Tanriover et al. (2003) 50 - - 44 88.0% 6 12.0% - -

Tanriover et al. (2004) 43 - - 38 88.4% 5 11.6% - -

Pai et al. (2005) 10 - - 8 80.0% - - - -

Vuillier et al. (2008) 100 17 17.0% 73 73.0% 9 9.0% - -

Nowinski et al. (2009) - - - - 78.0% - 12.0% - -

Ogeng'o et al. (2011) 288 18 6.3% 237 82.3% 31 10.8% 2 0.7%

Sadatomo et al. (2013) 124 - - 115 92.7% 9 7.3% - -

2.2.3. Early branching

Early branching can be defined as branching within the first 5 mm from the origin of the MCA117-120. It

has also been defined as branching that occurs within the proximal half of the M1 segment130. Teal et

al.117 observed three cases of early branching, one branched at 3 mm and two branched at 4 mm from

the origin of the MCA. Early branching has been reported in 2.7% (one case)125 3.3% (five cases)32,

5.1% (nine cases)118, 5.2% (15 cases)119, 5.3% (eight cases)131 and 11.3% (five cases)82 of cases in the

literature. Early branching can be observed unilaterally or bilaterally46.


The MCA cortical branches include the orbitofrontal artery (OfA), prefrontal artery (PfA), precentral

artery (PcA), central artery (CA), anterior and posterior parietal arteries, the angular artery (AA), the

temporal arteries (temporopolar, anterior, middle and posterior temporal arteries) and temporo-occipital

artery (ToA). These cortical branches can arise from the M1 segment and from the trunks that are formed

by bifurcation or trifurcation12. The most common origins of the MCA cortical branches are illustrated

in Figure 2.7.


24

Figure 1.7: Illustration of the most common origins of the cortical branches originating from the

superior, inferior and middle trunk (grey illustrates more than one typical origin).

(AA) Angular artery; (APA) Anterior parietal artery; (ATA) Anterior temporal artery; (CA) Central

artery; (MTA) Middle temporal artery; (OfA) Orbitofrontal artery; (PcA) Precentral artery; (PfA)

Prefrontal artery; (PPA) Posterior parietal artery; (PTA) Posterior temporal artery; (ToA) Temporo-

occipital artery; and (TpA) Temporopolar artery.

2.2.4.1. Origins

If bifurcation occurs, the superior trunk usually gives rise to the OfA, prefrontal, precentral and central

arteries, while the inferior trunk usually gives rise to the temporal and temporo-occipital arteries. The

parietal and angular arteries can arise from the superior or the inferior trunk. In the case of the trifurcation

pattern, the superior trunk usually gives rise to the OfA and prefrontal arteries, while the middle trunk

usually gives rise to the parietal and angular arteries. The precentral and central arteries can originate

from either the superior or the middle trunk. The inferior trunk usually gives rise to the temporal and

temporo-occipital arteries8, 11, 13, 27, 114, 121, 123, 132.

2.2.4.2. Early branches

Cortical branches that arise prior to the initial branching are referred to as early branches7, 8. The early

branches can be divided into early temporal branches (ETB) and early frontal branches (EFB)6, 7, 113, 119,

133. Gibo et al.7 observed 17 cases (34.0%) of ETB and five cases (10.0%) of early frontal branches,

while Ogeng'o et al.119 observed 184 cases (63.9%) of ETB and 104 cases (36.1%) of early frontal

branches. The OfA, temporopolar artery and anterior temporal artery (ATA) commonly originate as early

branches7, 8.


25

Türe et al.112 defined four configurations of early branches. In Type A only early temporal branches are

present, in Type B both the frontal and temporal early branches are observed, and in Type C only early

frontal branches are present. The Type D configuration is classified when no early branches are present.

Rhoton8 stated that there is usually only one early branch present, while Ciszek et al.133 stated that an

early frontal branch was most frequently located between two early temporal branches.

2.2.5. Anomalies

True anomalies of the MCA occur less frequently compared to anomalies of the other cerebral arteries7,

12, 113, 115, 117, 122, 134-136. The most common MCA anomalies include fenestration, and presence of a

duplicated or an accessory middle cerebral artery (Fig. 2.8). An additional branch is present with both

the duplicated and accessory middle cerebral arteries; an accessory MCA originates from the anterior

cerebral artery, while a duplicated MCA arises from the internal carotid artery (ICA)7, 11, 13, 41, 117. The

duplicated MCA usually supplies the temporal lobe and the accessory MCA typically supplies the frontal

lobe46, 115, 120, 136-139.


26

Figure 1.8: Anomalies of the middle cerebral artery. A) Accessory MCA from proximal A1

segment; B) Accessory MCA from middle A1 segment; C) Accessory MCA from distal A1

segment; D) Accessory MCA from AcoA level; E) Accessory MCA from A2 segment; F)

Duplicated MCA Type A; G) Duplicated MCA Type B; H) Proximal M1 fenestration; I)

Intermediate M1 fenestration; J) Distal M1 fenestration; and K) M2 segment fenestration.

(AChA) Anterior choroidal artery; (AcoA) Anterior communicating artery; (ICA) Internal carotid

artery; and (MCA) Middle cerebral artery.

Anomalies and variations can have serious clinical implications, therefore it is important to be aware of

possible variants. The knowledge of these variations can be helpful to neurosurgeons and clinicians10. If

the middle cerebral artery is occluded the accessory or duplicated MCA can offer potential collateral

supply, however, the supply may not be adequate to completely avoid ischemia33, 117, 119, 140.

2.2.5.1. Duplicated middle cerebral artery

The duplicated MCA can be classified into two types with regards to origin and diameter. The Type A

duplicated MCA (most common) has a similar diameter compared to the main middle cerebral artery

and arises at the top of the ICA (more distal origin). In Type B the duplicated MCA has a smaller

diameter compared to the main middle cerebral artery and arises between the top of the ICA and anterior

choroidal artery (more proximal origin)141-143. Type A can be viewed as an anomalous early arising MCA


27

trunk, and Type B as an anomalous early arising MCA branch144. The two types are illustrated in Figure

2.8F and G. Most authors do not state the exact origin of the duplicated MCA, or whether Type A or

Type B was observed.

The duplicated MCA was observed in 0.3% to 7.1% (Table 2.7)6, 32, 33, 53, 116, 118, 119, 122, 123, 130, 131, 144-150

of cases in the literature. Kobari et al.134 observed a triplicated MCA, with all three branches originating

from the internal carotid artery. Lame et al.151 observed a “crossover” duplicated MCA that originated

from the left internal carotid artery and supplied the right hemisphere. Kai et al.141 proposed that Type

B might be more susceptible to aneurysm formation.

2.2.5.2. Accessory middle cerebral artery

The accessory MCA is typically smaller compared to a duplicated middle cerebral artery and supplies a

smaller area152. The additional branch usually originates from the A1 segment close to the origin of the

AcoA6-8, 121, 140, 145, 153. Accessory middle cerebral arteries can be classified into five types depending on

the region of the ACA it arises from (Fig. 2.8A to E). The branch can arise from the proximal, middle or

distal A1 segment, at the AcoA level, or from the A2 segment.

Uchino et al.148 observed five cases with an accessory middle cerebral artery, four originating from the

proximal A1 segment and one from the distal A1 segment. Kim et al.150 observed one case arising from

the proximal part and two cases originated from the distal part of the A1 segment. Few authors have

described the accessory MCA originating from regions other than the proximal and distal A1 segment.

Kim and Lee154 stated that the accessory MCA originated from the middle A1 segment in two cases.

This artery rarely arises from the A2 segment135, 155 although Kim and Lee154 observed this in one case.

Additionally, Kahilogullari and Ugur156 observed an accessory MCA that originated from the

callosomarginal artery.

The accessory MCA was present in 0.1% to 9.1% (Table 2.7)6, 32, 33, 36, 53, 55, 56, 82, 99, 105, 106, 113, 114, 116, 121-

123, 130, 145, 147, 148, 150, 154, 157, 158 of cases. Two accessory middle cerebral arteries can also be present in one

hemisphere159 and Kim and Lee154 observed one case of bilateral accessory MCAs. Gibo et al.7 and

Kitami et al.147 observed a hemisphere with both an accessory and a duplicated MCA.

Takahashi et al.160 proposed that the accessory MCA is a larger recurrent artery of Heubner (RaH),

although this definition is no longer accepted8, 11, 13, 137. The RaH and the accessory middle cerebral artery


28

often originate from the same segment; however, the RaH terminates in the anterior perforated substance,

while the accessory MCA terminates as cortical branches7. Furthermore, the accessory MCA usually

gives off perforators, whereas the RaH ends as a perforator11, 13.


A fenestrated vessel has a common origin, splits into two channels and re-joins46, 58, 92-94. Fenestrations

can be small slit-like or large convex-like95, 161 and small slit-like fenestrations are most frequently

observed131, 162. Fenestration of the MCA is usually observed in the M1 segments, although it can also

be found in the M2 segment (Fig. 2.8K). Three types of M1 segment fenestrations can be defined;

proximal, intermediate and the distal type (Fig. 2.8H, I and J). The proximal fenestration is the most

common41, 95, 101, 115, 148, 150, 163-168. Fenestration of the MCA was observed in 0.1% to 5.8% (Table 2.7)53,

58, 93, 107, 120, 122, 124, 125, 145, 148, 150, 161, 168 of cases. In previous studies the temporopolar artery commonly

originates as an early temporal branch in association with fenestrations46, 52, 93, 95, 115, 120, 150, 168, 169.


29

Table 1.7: The prevalence of fenestration, duplicated and accessory middle cerebral arteries6, 32, 33,

36, 53, 55, 56, 58, 82, 93, 99, 105-107, 113, 114, 116, 118-125, 130, 131, 144-150, 154, 157, 158, 161, 168.

Total Duplicated MCA Accessory MCA Fenestration

Cases % Cases % Cases %

Crompton (1962) 347 10 2.9% 1 0.3% 1 0.3%

Jain (1964) 300 2 0.7% 8 2.7% - -

Wollschlaeger et al. (1967) 582 - - - - 1 0.2%

Ito et al. (1977) 1129 - - - - 3 0.3%

Grellier et al. (1978) 280 1 0.4% 3 1.1% - -

Milenković (1981) 60 1 1.7% - - - -

Kayembe et al. (1984) 44 - - 4 9.1% - -

Kayembe et al. (1984) 146 - - 10 6.8% - -

Umansky et al. (1984) 70 - - 2 2.9% - -

Atunes (1985) 37 - - - - 1 2.7%

Kitami et al. (1985) 704 6 0.9% 4 0.6% 4 0.6%

Tran-Dinh (1986) 150 - - 3 2.0% - -

Umansky et al. (1988) 104 1 1.0% 2 1.9% 1 1.0%

Yamamoto et al. (1992) 455 7 1.5% 14 3.1% - -

Sanders et al. (1993) 5190 - - - - 9 0.2%

Meneses et al. (1997) 14 1 7.1% 1 7.1% - -

Ozaki et al. (1997) 153 2 1.6% 9 5.9% - -

Uchino et al. (2000) 425 9 2.1% 5 1.2% 2 0.5%

Gailloud et al. (2002) 1170 - - - - 5 0.4%

Idowu et al. (2002) 100 - - 1 1.0% - -

Tanriover et al. (2003) 50 1 2.0% 2 4.0% - -

Uchino et al. (2003) 900 14 1.6% - - - -

Karazincir et al. (2004) 176 1 0.6% - - - -

Tanriover et al. (2004) 43 - - 2 4.7% - -

Kim et al. (2005) 448 2 0.4% 2 0.4% 2 0.4%

Kim et al. (2005) 743 6 0.8% 1 0.1% 1 0.1%

D’Ávila & Schneider

(2006)

50 - - 1 2.0% - -

Bharatha et al. (2008) 504 - - - - 2 0.4%

Vuillier et al. (2008) 100 - - - - 3 3.0%

Gielecki et al. (2009) 304 2 0.7% - - - -

Kim & Lee (2009) 1250 - - 16 1.3% - -

van Rooij et al. (2009) 208 - - - - 12 5.8%

Bayrak et al. (2011) 395 - - - - 4 1.0%

Chang & Kim (2011) 1250 9 0.7% - - - -

Chang & Kim (2011) 1452 9 0.6% - - - -

Chang & Kim (2011) 2527 7 0.3% - - - -

Ogeng'o et al. (2011) 288 5 1.7% - - - -

Sun et al. (2012) 4652 - - - - 3 0.06%

Uchino et al. (2012) 3491 - - - - 3 0.09%

Hamidi et al. (2013) 500 7 1.4% 1 0.2% 10 2.0%

Cooke et al. (2014) 10927 - - - - 10 0.09%

Kovač et al. (2014) 455 - - - - 1 0.2%

van Rooij et al. (2015) 140 - - - - 4 2.9%


30

Some authors observed an association between aneurysms and a duplicated MCA143, 170, 171, although

very few have observed aneurysms at the origin or near the abnormal vessel136, 141, 172-176. Selected

authors138, 139, 153, 155, 177-180 observed an association between aneurysms and an accessory MCA. Few

studies159, 181-188 have, however, reported aneurysms at the origin or near the vessel.

Fenestration might predispose patients to aneurysm formation171 and certain authors have reported an

association between aneurysms and fenestration (proximal or distal to the fenestration)55, 98, 165, 171, 189-

192. Very few studies have, however, observed aneurysms at the site of the MCA fenestration168, 193-195.

Furthermore, van Rooij et al.161 stated that fenestrations with and without aneurysms were not

statistically significantly different.


31

2.3. POSTERIOR CEREBRAL ARTERY

The posterior circulation is complex, tends to vary and very few studies have been conducted on the

anatomy of the posterior cerebral artery (PCA)9. The PCA is the terminal branch of the basilar artery,

originating anterior to the midbrain11, 12. There are four segments that can be described separately (Fig.

2.9). These include the P1 or precommunicating segment, the P2 or ambient segment, the P3 or

quadrigeminal segment and the P4 or calcarine segment12, 13, 196.

2.3.1. Segments

The proximal PCA refers to the P1 segment and the distal PCA refers to the part after the origin of the

posterior communicating artery (PcoA). Very few studies focused on the anatomy of the PCA and the

distal segment and cortical branches have particularly been neglected197. These segments are illustrated

in Figure 2.9.

Figure 1.9: The different segments and cortical branches of the posterior cerebral artery

(Adapted from Bradac13). (AITA) Anterior inferior temporal artery; (CA) Calcarine artery; (MITA)

Middle inferior temporal artery; (PITA) Posterior inferior temporal artery; (PcoA) Posterior

communicating artery; and (PoA) Parieto-occipital artery.

The P1 segment ends at the origin of the PcoA and the P2 segment extends from the junction of the PcoA

to the posterior part of the midbrain12. The P2 segment can be subdivided into an anterior and posterior

part, the P2A and P2P segments. The P2A segment extents from the PcoA and enters the proximal part

of the ambient cistern. The P2P segment begins at the posterior margin of the cerebral peduncle198-200.

Párraga et al.201 stated that the most prominent, lateral aspect of the peduncle is an easier visualized point


32

of division. The transition point between the P2A and P2P segments has also been described as the lateral

mesencephalic sulcus201.

The P3 segment is the continuation of the PCA within the perimesencephalic cistern. The P2 and P3

segment transition point has been described as the origin of the anterior inferior temporal artery (AITA),

however, this point may vary201. The P3 segment often divides into terminal branches before ending at

the calcarine fissure and the P4 segment originates at the anterior limit of the calcarine fissure12, 199. The

parieto-occipital and calcarine arteries can run together for a short distance before bifurcating (early

bifurcation)201.

2.3.2. Cortical arteries

The PCA cortical branches include the anterior inferior temporal artery (AITA), middle inferior temporal

artery (MITA), posterior inferior temporal artery (PITA), calcarine artery (CA), parieto-occipital artery

(PoA) and in some cases a splenial artery (SA). These cortical branches can arise from the P2, P3 or P4

segments. The temporal arteries can also originate from a common trunk, the common temporal artery

(CTA). These cortical branches can be absent, duplicated or triplicated12, 199.

2.3.2.1. Temporal arteries

The temporal arteries (anterior, middle and posterior temporal arteries) can originate from the main trunk

of the PCA, or from the common temporal artery. The CTA can also be referred to as the lateral occipital

artery, the lateral division of the PCA or the temporo-occipital artery. This should not be confused with

the MCA cortical branch, the temporo-occipital artery12, 199, 202, 203. The CTA usually originates from the

P2 segment at the level of the lateral geniculate body202.

The temporal arteries usually arise from the P2 segment (Table 2.8)12, 146, 196, 199, 202. Several authors199,

202 have reported the MITA as the least consistent cortical branch of the PCA, and certain authors do not

even describe this cortical branch196. Duplication of the PITA was present in 2.8% (one case)202, 6.0%

(three cases)199 and 7.5% (three cases)196 of specimens. Three or more posterior inferior temporal arteries

have been observed in 12.5% (five cases)196 in the literature.


33

Table 1.8: Origins of the temporal and common temporal arteries199, 204.

CTA AITA MITA PITA

Authors Zeal &

Rhoton

(1978)

Haegelen

et al.

(2012)

Zeal &

Rhoton

(1978)

Haegelen

et al.

(2012)

Zeal &

Rhoton

(1978)

Haegelen

et al.

(2012)

Zeal &

Rhoton

(1978)

Haegelen

et al.

(2012)

Total 50 40 50 40 50 40 50 40

Presence 16.0% 20.0% 84.0% 80.0% 38.0% 20.0% 96.0% 80.0%

P2 segment: - - - - - - - -

P2A 37.5% 50.0% 76.2% 93.8% 42.1% 50.0% 4.2% 18.8%

Junction - 12.5% - 3.1% - 12.5% - 12.5%

P2P 62.5% 37.5% 23.8% 3.1% 57.9% 37.5% 89.6% 68.8%

P3 Segment - - - - - - 6.3% -

(AITA) Anterior inferior temporal artery; (CTA) Common temporal artery; (MITA) Middle inferior temporal artery; and (PITA) Posterior

inferior temporal artery.



34

The arteries that supply the temporal lobe were classified into five groups by Zeal and Rhoton199. The

different groups are described in Table 2.9 and the frequencies observed by Zeal and Rhoton199, Párraga

et al.201 and Haegelen et al.204 are given.

Table 1.9: The prevalence of the temporal artery configurations199, 201, 204.

Description Zeal &

Rhoton

(1978)

Párraga

et al.

(2011)

Haegelen

et al.

(2012)

Group 1 Present: AITA, MITA, PITA, hippocampal arteries

10.0% 36.0% 7.5%

Group 2

Present: CTA 16.0% 23.0% 20.0%

Group 3 Present: AITA, MITA, PITA

Absent: hippocampal arteries

20.0% 8.0% 10.0%

Group 4 Present: AITA, PITA

Absent: MITA, hippocampal arteries

10.0% 7.0% 47.5%

Group 5 Present: AITA, PITA, Hippocampal arteries

Absent: MITA

44.0% 26.0% 15.0%

(AITA) Anterior inferior temporal artery; (CTA) Common temporal artery; (MITA) Middle inferior

temporal artery; and (PITA) Posterior inferior temporal artery.

Haegelen et al.204 proposed a new classification for the inferior temporal arteries of the PCA. In Type 1,

anterior and posterior temporal arteries were present. In Type 2 the anterior hippocampal, anterior and

posterior temporal arteries were present. In the Type 3 the common temporal artery was present. This

was observed in 57.5%, 22.5% and 20.0% of cases, respectively204.

2.3.2.2. Splenial artery

The SA supplies the splenium of the corpus callosum and can also be referred to as the posterior

pericallosal artery88, 199, 203. The splenial artery usually arises from the parieto-occipital artery or the main

stem of the PCA (Table 2.10)203. Duplication of the splenial artery can be observed and Türe et al.88

stated that in 25.0% (10 cases), an accessory splenial artery was present. Zeal and Rhoton199 observed

the SA in all hemispheres; however, Margolis et al.196 observed the SA in only 35.0% of 40 hemispheres.

The SA can anastomose with branches of the pericallosal artery anterior to the splenium199.


35

2.3.2.3. Terminal trunks

The parieto-occipital artery and the calcarine artery are the two terminal trunks of the PCA12. In a study

by Zeal and Rhoton199 on 50 hemispheres, the PoA was the terminal branch in 56.0% and in 44.0% the

PCA terminated as the calcarine artery. The parieto-occipital and calcarine arteries supply the posterior

third of the brain at the longitudinal fissure and part of the parietal and occipital lobes12.

The origin of the calcarine artery is usually similar to the origin of the parieto-occipital artery since it

usually arises from the same distal part of the PCA202. These cortical branches usually originate from the

P3 segment (Table 2.10). Duplication of the calcarine artery was observed in 10.0% (five cases)199,

20.0% (12 cases)202 and 60.0% (24 cases)196.


36

Table 1.10: Origins of the splenial, parieto-occipital and calcarine arteries88, 196, 199, 201.

SA PoA CA

Authors Zeal &

Rhoton

(1978)

Türe

et al.

(1996)

Párraga

et al.

(2011)

Margolis

et al.

(1971)

Zeal &

Rhoton

(1978)

Párraga

et al.

(2011)

Margolis

et al.

(1971)

Zeal &

Rhoton

(1978)

Párraga

et al.

(2011)

Total 50 40 70 40 50 70 40 50 70

Present: 100% 100% 90.0% - 96.0% 100% - 100% 91.4%

P2 segment: - 2.0% - 38.0% - - 16.0% - -

P2A - - - - 10.0% - - - -

P2P 4.0% - - - 40.0% 1.4% - 42.0% -

P3 segments 4.0% 32.0% 30.2% 22.0% - 71.4% 23.0% 48.0% 64.3%

P4 segments - - 3.2% 40.0% - 27.1% 39.0% - 27.1%

PoA 62.0% 52.0% 50.8% - - - 16.0% 10.0% 8.6%

CA 12.0% 7.0% - - - - - - -

PITA 6.0% - - - - - - - -

CTA - 7.0% - - - - - - -

MPChA/ LPChA 12.0% - 15.9% - - - - - -

(CA) Calcarine artery; (CTA) Common temporal artery; (PITA) Posterior inferior temporal artery; (PoA) Parieto-occipital artery; and (SA)

Splenial artery.



37

The parieto-occipital artery usually divides into a few different branches that either runs deep into the

parieto-occipital fissure or the medial surface of the parieto-occipital lobe196, 202, 203. Duplication was

observed in 1.7% (one case)202 and 5.0% (one case)196 in the literature.

2.3.2.4. Diameter and Lengths

The diameter and lengths of the PCA segments and cortical branches have not been thoroughly studied.

The diameters and the length of the PCA segments, as reported in the literature9, 200, are given in Table

2.11. There are limited reports on the diameter and length of the PCA cortical branches.

Table 1.11: The average diameter (mm) and length (mm) of the posterior cerebral artery

segments9, 200.

Diameter Length

Kawashima et al. (2005b) Pai et al. (2007)

R L

P2 Segment - 19.9 mm (12-28 mm) 18.44 mm (10-28 mm)

P2A

Segment

2.1 mm ± 0.4 mm - -

P2P Segment 1.7 mm ± 0.3 mm - -

P3 Segment 1.7 mm ± 0.2 mm 22.4 mm (13-38 mm) 20.9 mm (13-38 mm)

2.3.3. Branching pattern

The end of the main trunk has previously been described at the branching of the common temporal artery;

however, the main trunk is now understood to end at the origin of the calcarine and parieto-occipital

arteries. The level at which the main trunk terminates can differ. It typically divides at the P3 segment

although the main trunk can run into the calcarine fissure and branch at the P4 segment. The main stem

can be referred to as the medial occipital artery205.

Three branching patterns of the distal PCA have been described by Milisavljević et al.197. In Type 1 the

terminal division is at the P3 or P4 segment. In Type 2 the terminal division is at the P3 or P4 segment

with the common temporal artery present. In Type 3 the terminal division is at the P2 segment (early

branching). In 70 hemispheres, Milisavljević et al.197 observed Type 1, Type 2 and Type 3 in 42.9%,

41.4%, and 15.7% of cases, respectively.


38

2.3.4. Anomalies

The cortical branches can either be absent, duplicated or triplicated. The origins of the arteries can exhibit

typical variation; additionally, the cortical branches can also have abnormal origins. This includes the

parieto-occipital, calcarine and posterior temporal arteries originating from the ICA12. Choi et al.206 and

Buxton and Cook207 observed a rare case of the parieto-occipital artery originating from the ICA.

Bergquist208 observed a case of the PITA that originated from the internal carotid artery. True anomalies

of the PCA include duplication, triplication and fenestration of the main stem of the PCA. The prevalence

of the PCA anomalies are summarised in Table 2.12.

Table 1.12: The prevalence of the posterior cerebral artery anomalies36, 53, 60, 62, 69, 99, 105, 107, 118, 146,

161, 197, 205, 209-213.

Total Fenestration Duplication Triplication

Cases % Cases % Cases %

Windle (1888) 200 - - 3 1.5% - -

Fisher (1965) 414 - - 1 0.2% - -

Milenković (1981) 60 - - 1 1.7% - -

Bartosiak et al. (1983) 50 - - 1 2.0% - -

Bisaria (1984) 252 - - 1 0.4% - -

Milisavljević et al. (1988) 70 1 1.4% - - - -

Caruso et al. (1991) 100 1 1.0% 1 1.0% - -

Karazincir et al. (2004) 176 1 0.6 - - - -

Ladziński & Maliszewski (2005) 100 - - 1 1.0% - -

Kapoor et al. (2008) 1000 - - 23 2.3% 8 0.8%

van Rooij et al. (2009) 208 2 1.0% - - - -

Bayrak et al. (2011) 395 2 0.5% - - - -

Sun et al. (2012) 4652 1 0.02% - - - -

Hamidi et al. (2013) 500 7 1.4% 1 0.2% - -

Cooke et al. (2014) 10927 167 0.01% - - - -

Kovač et al. (2014) 455 - - 1 0.2% - -

Gunnal et al. (2015) 340 3 0.9 5 1.5 - -

Vlajković et al. (2015) 468 4 0.9% - - - -


Fenestration occurs when the lumen of an artery is divided into two segments. It can also be referred to

as partial duplication. A fenestrated vessel has a common origin, splits into two channels and re-joins46,

58, 92-94. Fenestration of the PCA is extremely rare. The majority of these fenestrations are observed in

the P1 segment; however, fenestrations can also be observed in either the P2 segment or the distal

posterior cerebral artery41, 45, 46, 107, 211, 214. The mechanisms of the formation of PCA fenestrations are


39

still unclear45, 46. Fenestrations in the posterior cerebral artery were observed in 0.01% to 1.4% (Table

2.12)53, 99, 105, 107, 118, 161, 197, 211-213 of cases in previous studies. Most PCA fenestrations were reported as

case studies214 -218.

2.3.4.2. Duplicated and triplicated posterior cerebral arteries

The P1 and P2 segments can both be duplicated; however, the P1 segment is more commonly

duplicated211. Kapoor et al.62 reported that the additional branch originated from the P1 segment and ran

mostly parallel to the main PCA. Kapoor et al.62 describes duplication of the PCA as one branch arising

from the PcoA and one from the basilar artery with a short junction between the two arteries. Early

branching of the PCA was also described and this can present as duplication208. Duplication of the PCA

was observed in 0.2% to 2.3% (Table 2.12)36, 53, 60, 62, 69, 146, 205, 209-212 of cases. Most PCA duplications

were reported as case studies219, 220. Duplication and triplication of the PCA are illustrated in Figure 2.10.

Figure 1.10: Anomalies of the posterior cerebral artery62. A) Duplication; and B) Triplication.

Few studies have reported triplication of the PCA. Kapoor et al.62 observed triplication of the PCA in

0.8% (eight cases). Kapoor et al.62 described three branches arising from the P1 segment that supplied

the occipital and temporal lobes, although the middle branch tended to be very small.


40

CHAPTER THREE

PROBLEM STATEMENT, AIM,

OBJECTIVES

3 AIM, OBJECTIVES, HYPOTHESIS


41

3.1. PROBLEM STATEMENT

Possible differences in the diameter and length of the cerebral segments and cortical branches between

age, population groups, sex and bilateral variation are, to the author’s best knowledge, not mentioned or

poorly reported in previous studies. Few studies give a complete description of the origins of the cortical

arteries and reports on the diameter, length, absence, duplication and triplication are also limited. The

MCA branching subtypes were mostly overlooked, only bifurcation and trifurcation is usually noted.

The branching of the PCA has not been adequately described. The level of the PoA and CA origin is

usually noted; however, whether branching is observed before the origin of these cortical branches is not

mentioned. Anomalies of the cerebral arteries are usually only mentioned; few reports exist on the

specific origin, length, diameter and cortical arteries that arise from these anomalous branches.

3.2. AIM

The aim of this study is to describe the anatomy and anomalies of the cerebral vasculature in a Southern

African cadaver cohort.

3.3. OBJECTIVES

To perfuse the anterior, middle and posterior cerebral arteries with a coloured silicone;

To create digital images of the cerebral vasculature;

To note origins, branching patterns and arterial variations;

To measure the diameter and length of the vessels; and,

To compare the results with the literature.


42

CHAPTER FOUR

MATERIALS AND METHODS

4 MATERIALS AND METHODS


43

4.1. STUDY POPULATION

The National Health Act, No 61 of 2003 (sections 61 to 64)221, states that human cadavers may be used

for anatomical dissection and research in South Africa. Ethical clearance (S14/05/100) was obtained

from the Health Research Ethics Committee (HREC) at Stellenbosch University. A pilot study was done

on 10 specimens to ascertain the most effective method and agent for arterial perfusion. Embalmed

cadavers (n=100) were used for the present study. According to the Death Certificates, the individuals

died of causes unrelated to brain trauma since damage or lesions could influence the results. Previous

studies21, 78 excluded specimens that showed damage or brain trauma. Brains that were too degraded (due

to an extended period between death and embalming) or damaged (during removal of brains), were

excluded, resulting in 63 specimens suitable for use for the present study.

When only a section of the brain was damaged during removal, that specific cerebral artery was

excluded. One-hundred hemispheres were used for the MCA, 121 hemispheres for the ACA and 124

hemispheres for the PCA. The total of 126 hemispheres consisted of males (n=88) and female (n=38)

specimens between the ages of 22 and 84 (average 44 years of age). The specimens were distributed over

three population groups, coloured (n=76), black (n=38), white (n=10) and unknown (n=2). This is

tabulated in Table 4.1. Ten brains (20 hemispheres) were used for the pilot study, although, the ACA of

one hemisphere was excluded due to damage during removal of the brain.


44

Table 4.1: Study population information.

TOTAL ACA MCA PCA

Total 126 121 100 124

Bilateral Right 63 60 50 62

Left 63 61 50 62

Sex Male 88 83 68 86

Female 38 38 32 38

Population Groups Coloured 76 72 56 74

Black 38 37 34 38

White 10 10 8 10

Unknown 2 2 2 2

Age Groups <34 40 36 28 38

35-48 36 35 29 36

49> 40 40 33 40

Unknown 10 10 10 10

Minimum 22 22 22 22

Maximum 84 75 75 84

Average 44 45 45 45

(ACA) Anterior cerebral artery; (MCA) Middle cerebral artery; and (PCA) Posterior cerebral artery.

4.2. REMOVAL OF THE BRAIN

The scalp was reflected by making an incision from the nasion to the inion and from the vertex towards

each ear bilaterally. The periosteum and temporalis muscle were reflected inferiorly. Using an oscillating

bone saw (HEBU Medical, Oscillating Saw), the calvaria were cut from the supraorbital margin to the

inion. The falx cerebri was separated from the crista galli and from the tentorium cerebelli. The optic,

trochlear, abducent, trigeminal and oculomotor nerves were severed as well as the internal carotid

arteries and pituitary stalk. The facial, hypoglossal, vagus, glossopharyngeal, accessory and

vestibulocochlear nerves were then severed and the spinal cord was cut222. After removal of the brain,

the specimens were placed in five litre buckets (containing 10% buffered formaldehyde) before perfusion

of the cerebral arteries.

4.3. PREPARATION OF THE SPECIMENS

The arachnoid mater was removed to expose the Circle of Willis. The AcoA, posterior communicating

arteries and the A1 segments (at the proximal origin) were clamped (indicated in green in Fig. 4.1). The


45

A1 segments were severed proximal to the origin of the AcoA and the P1 segments were cut before the

origin of the PcoA (indicated in red in Fig. 4.1).

Figure 4.1: Perfusion of the cerebral arteries. Arrows indicate the position of insertion of the

catheter, the red lines indicates the position where vessels were severed and the green lines indicate the

sites of clamping.

The A1 segments, internal carotid arteries and P1 segments were cannulated with a plastic catheter

(Vasofix® Safety 18 gage, B. Braun) (indicated as blue arrows in Fig. 4.1). An isotonic saline solution

was injected (using a 1 mm syringe) into the arteries to remove any blood or blood clots3, 21, 29, 57, 88, 200,

223, 224. The arteries were then injected with coloured silicone (MM922 Silicone, ACC Silicone

Concepts). The entire arterial system could be injected with the same colour, or the cerebral arteries

could be cannulated separately2. Injecting the left and right anterior cerebral arteries with different colour

allows visualization of any anastomoses between the two hemispheres3. In the current study each

cerebral artery was injected with a different colour solution to assist in visualization of possible

anastomoses between cerebral arteries.

Perfusion mediums used in similar studies include coloured silicone16, 29, 30, 115, 200, 201, coloured latex or

acrylic2, 5, 6, 7, 14, 17, 28, 57, 78, 88, 121, 156, 157, 199, 204, 205, 225 and a mixture of India ink and gelatin3, 7, 84, 200, 226. In

two studies9, 127 the vessels were painted with water colour after dissection. Additional substances used

include wax, varnish, coloured dyes, paint, barium sulphate, olive oil, Prussian blue, carmine, methyl


46

methacrylate and acryplastic injection121, 226, 227. When pigment is added the smaller branches are easily

identified and differentiated from the arachnoid strands127.

After perfusion, the specimens were stored in 10% buffered formaldehyde solution for at least two weeks

before the cerebral arteries were dissected. In previous studies, most authors used specimens that were

fixed with formaldehyde5, 10, 21, 22, 29, 32, 57, 67, 78, 87, 88, 91, 115, 157, 196, 199-201, 204, 205, 223, 225 although selected

authors preferred to work with unfixed specimens121, 228. After completion of perfusion, digital images

(using Canon IXUS 220 HS) were taken.

The ACA configuration was first examined at the interhemispheric region to observe any anastomoses

between the two hemispheres. If there were any branches crossing from one hemisphere to the other, the

anatomical details were recorded. The two hemispheres were then separated, with the use of a scalpel,

at the corpus callosum to view the medial surface of the brain3. The temporal lobe was moved laterally

to allow visualization of the middle cerebral artery5. Digital images were taken of the medial and lateral

surface of each hemisphere.

4.4. MEASUREMENT OF THE VESSELS

The external diameter and length of all the cortical branches were measured using a digital micrometre.

The diameter was measured at the origin of the branch and the lengths of the ACA cortical branches

were measured from the origin of the branch to the AcoA3, 16. The length of the MCA cortical branches

was measured from the origin of the middle cerebral artery to the origin of the branch, and the length of

the PCA cortical branches was measured from the origin of the PCA to the origin of the branch.

Measurements by previous authors were made using digital callipers16, 29, 78, 135, Vernier callipers87, under

magnification6, 14, 28, 199, 229, ocular micrometre223 and using the software “Image J”230. A calibrator and

measuring tape have also been used201.

4.5. STATISTICAL ANALYSIS

The diameter and length were measured three times, and a scatterplot was drawn to illustrate that there

were no statistically significant differences between the measurements. The diameter and lengths of the


47

cortical branches were compared using Mixed-effects REML regression. The statistical analysis was

performed using the software, Statistica® Version 12.0 (StatSoft Inc. 2014, USA). A comparison was

made between the left and right sides, sex, population groups and different age groups.


48

CHAPTER FIVE

RESULTS

5 RESULTS


49

5.1. PILOT STUDY: ANTERIOR CEREBRAL ARTERY

A pilot study (n=19) was done to assess the anatomy of the ACA and its branches. The most common

variations were either complete absence or duplication of an artery. The diameter and length of the ACA

cortical branches were measured. Any absence, duplications or triplications were reported and the origins

of the branches were noted (Table 5.1).

The infra-orbital artery and the FpA were absent in eight cases (42.1%) and nine cases (47.4%),

respectively, and the anterior, middle and posterior internal frontal arteries were always present.

Furthermore, the AIFA and PIFA were duplicated in one case each. The MIFA was the most consistent

artery; it was always present and never duplicated. The paracentral lobule artery was the most frequently

duplicated (36.8%) vessel. The superior and inferior internal parietal arteries were absent in two cases

(10.5%) and five cases (26.3%), respectively, and the IIPA was duplicated in one case. The

callosomarginal artery and the IFA were both observed in only 31.6% of cases in the pilot study.

Moreover, the callosomarginal artery and IFA were only present in the same hemisphere in one case.

There were no triplicated cortical branches.


50

Table 5.1: The average diameter (mm), average length (mm), presence, duplication, triplication and origins of the anterior cerebral

cortical branches observed in the pilot study.

IfO FpA AIFA MIFA PIFA IFA PLA SIPA IIPA CmA

Presence 57.9% 52.6% 100% 100% 100% 31.6% 100% 89.5% 73.7% 31.6%

Duplication - - 5.3% - 5.3% - 36.8% - 5.3% -

Triplication - - - - - - - - - -

Diameter 1.1 1.0 1.3 1.3 1.4 1.6 1.3 1.1 1.0 1.8

Length 9.8 21.0 28.3 46.9 53.2 34.6 81.0 99.9 90.9 33.1

A2 Segment 90.9% 40.0% 30.0% - - 16.7% - - - 16.7%

A3 Segment - 20.0% 40.0% 47.4% 45.0% 66.7% 3.8% 5.9% - 83.3%

A4 Segment - - - - 10.0% - 42.3% 17.6% 13.3% -

A5 Segment - - - - - - 26.9% 64.7% 40.0% -

CmA - - 10.0% 21.1% 25.0% 16.7% 15.4% 5.9% - -

IFA 9.1% 10.0% 20.0% 21.1% 15.0% - - - - -

AIFA - 30.0% - 5.3% - - - - - -

MIFA - - - - - - - - - -

PIFA - - - 5.3% - - 7.7%

CT:3.8%

- - -

PLA - - - - CT:5.0% - - 5.9% - -

SIPA - - - - - - - - 6.7% -

PCA - - - - - - - - 40.0% -

(AIFA) Anterior internal frontal artery; (CmA) Callosomarginal artery; (CT) Common trunk; (FpA) Frontopolar artery; (IFA) Internal

frontal artery; (IfO) Infra-orbital artery; (IIPA) Inferior internal parietal artery; (MIFA) Middle internal frontal artery; (PIFA) Posterior

internal frontal artery; (PLA) Paracentral lobule artery; (PoA) Posterior occipital artery; and (SIPA) Superior internal parietal artery.



51

The IfO and frontopolar artery most commonly arose from the A2 segment, while the IFA, frontal

arteries and the CmA typically originated from the A3 segment. The paracentral lobule artery usually

arose from the A4 segment, and the SIPA from the A5 segment. The IIPA arose equally from the A5

segment and posterior cerebral artery. The IIPA originated from the posterior cerebral artery in 40.0%

of cases observed in the pilot study (Fig. 5.1); this was the most notable difference between the pilot

study and what was reported in the literature.

Figure 5.1: The inferior internal parietal artery originating from the posterior cerebral artery.

(CA) Calcarine artery; (IIPA) Inferior internal parietal artery; (PITA) Posterior inferior temporal

artery; (PoA) Parieto-occipital artery; and (SA) Splenial artery.

There were no azygos, bihemispheric or median anterior cerebral arteries observed in the pilot study,

and fenestration was also not observed. This shows the need for larger studies on the anterior circulation.

PoA

CA

IIPA

SA


52

5.2. PILOT STUDY: MIDDLE CEREBRAL ARTERY

A pilot study was conducted (n=20) to assess the anatomy of the MCA and its cortical branches. There

were no cases with fenestrations, accessory or duplicated middle cerebral arteries. The branching pattern

of the MCA was classified according to the 11 different types observed in the literature (Fig. 2.6). The

exact distances used to classify the different branching patterns were, however, not noted in previous

studies and had to be defined. Since early branching is classified as branching before 5 mm117-120, medial

and lateral branching were defined as branching between 5 mm and 20 mm, and branching after 20 mm,

respectively. Bifurcation was observed in 16 cases, and these cases were further divided into medial

bifurcation (50.0%), lateral bifurcation (25.0%) and lateral pseudobifurcation (5.0%). There were no

cases of medial pseudobifurcation. True trifurcation and pseudotrifurcation were not observed, although

two cases (10.0%) of proximal trifurcation and one case (5.0%) of distal trifurcation were observed.

Some studies have failed to differentiate between true trifurcation and pseudotrifurcation; this distinction

is, however, important to determine the true prevalence of these branching patterns. Tetrafurcation and

pseudotetrafurcation were not observed, however, one case of monofurcation was present.

There is considerable variation in the MCA cortical branches in terms of size, number and area supplied7.

The diameters and lengths of the different cortical branches are given in Table 5.2 as well as the

percentage of duplicated branches. The most commonly duplicated branch was the anterior parietal

artery in 30.0%. The most commonly absent cortical branch was the common temporal artery in 65.0%

and the temporal polar artery in 40.0%. There were no triplicated cortical branches.


53

Table 5.2: The average diameter (mm), average length (mm), presence, duplication, triplication and origins of the middle cerebral


OfA PfA PcA CA APA PPA AA ToA CTA TpA ATA MTA PTA

Presence 95.0 90.0 95.0 100 90.0 100 95.0 65.0 35.0 60.0 95.0 90.0 90.0

Duplication 15.0 5.0 25.0 25.0 30.0 15.0 5.0 - - - - - 5.0

Triplication - - - - - - - - - - - - -

Diameter 1.4 1.5 1.3 1.4 1.4 1.5 1.5 1.5 1.5 1.1 1.2 1.1 1.4

Length 33.1 43.3 63.5 65.0 74.6 90.9 90.0 81.6 33.7 33.0 38.7 61.9 66.0

EB 23.8% 22.2% - - - - - - 16.7% 54.5% 27.8% - 16.7%

INF - - - 4.3% 17.4% 40.9% 78.9% 91.7% 66.7% 27.3% 50.0% 47.1% 61.1%

SUP 47.6% 77.8% 95.7% 91.3% 78.3% 50.0% 21.1% 8.3% - - - - -

CTA - - - - - - - - - 18.2% 22.2% 29.4% 11.1%

PfA 28.6% - - - - - - - - - - - -

PcA - - - 4.3% - - - - - - - - -

CA - - 4.3% - 4.3% - - - - - - - -

AA - - - - - 9.1% - - - - - - -

ToA - - - - - - - - - - - 5.9% 11.1%

PTA - - - - - - - - 16.7% - - 17.6% -

Monofurcation was excluded for origins.

(AA) Angular artery; (APA) Anterior parietal artery; (ATA) Anterior temporal artery; (CA) Central artery; (EB) Early branches; (INF)

Inferior trunk; (MTA) Middle temporal artery; (OfA) Orbitofrontal artery; (PcA) Precentral artery; (PfA) Prefrontal artery; (PPA) Posterior

parietal artery; (PTA) Posterior temporal artery; (ToA) Temporo-occipital artery; (TpA) Temporopolar artery; and (SUP) Superior trunk.



54

Very few studies describe the origins of the cortical MCA branches, therefore the origins of the cortical

branches were noted in the pilot study and a detailed description is given in Table 5.2. The temporal and

temporo-occipital arteries usually originated from the inferior trunk, and the OfA, PfA, precentral and

central arteries typically originated from the superior trunk. The parietal arteries and angular artery

originated from either the superior or the inferior trunk.

Early frontal branches that were commonly observed included the OfA in 23.8% and the prefrontal artery

in 27.8% of cases. The TpA was most commonly observed as an early temporal branch in 54.5% of

cases. Common trunks between arteries occurred frequently. The PfA and precentral artery originated

as a common trunk in 42.1%, the temporopolar artery and ATA originated with a common trunk in

31.6%, and the PcA and central artery in 31.6% of cases.


55

5.3. PILOT STUDY: POSTERIOR CEREBRAL ARTERY

Twenty hemispheres were perfused with coloured silicone to assess the anatomy of the PCA. The

diameter and length of the PCA cortical branches were measured. Any absence, duplications or

triplications were reported and the origins of the branches were noted (Table 5.3). The most common

variations were either complete absence or duplication of an artery. The most frequently absent arteries

were the splenial artery in 16 cases (80.0%) and the common temporal artery in 14 cases (70.0%). Most

commonly duplicated was the calcarine artery in 25.0% (five cases) and the AITA was the only

triplicated artery (one case).

The P2A segment usually gave origin to the temporal arteries (anterior, middle and posterior inferior

temporal arteries) and the common temporal artery. The calcarine artery and PoA usually originated

from the P3 segment and the splenial artery usually originated from the parieto-occipital artery (50.0%).

The common temporal artery was present in only six cases; in three cases it gave origin to the MITA and

PITA, and in three cases it gave origin to all three temporal arteries. A complete description is given in

Table 5.3.


56

Table 5.3: The average diameter (mm), average length (mm), presence, duplication, triplication and origins of the posterior cerebral


CTA AITA MITA PITA CA PoA SA

Presence 30.0% 75.0% 95.0% 95.0% 100% 100% 20.0%

Duplication - 10.0% - 10.0% 25.0% 10.0% -

Triplication - 5.0% - - - - -

Diameter 2.0 1.0 1.3 1.6 1.2 1.5 0.8

Length 25.7 19.5 27.0 30.8 52.0 55.4 63.2

P2A 100% 77.8% 47.4% 52.4% 16.0% 13.6% -

P2P - - - 4.8% 24.0% 18.2% 25.0%

P3 - - - 4.8% 44.0% 54.6% -

P4 - - - - 8.0% 9.1% -

CTA - 11.1% 31.6% 28.6% - - -

MITA - - - 4.8% - - -

PITA - 11.1% 21.1% - 4.0% - 25.0%

CA - - - 4.8% - 4.6% -

PoA - - - - 4.0% - 50.0%

(AITA) Anterior inferior temporal artery; (CA) Calcarine artery; (CTA) Common temporal artery; (MITA) Middle inferior temporal artery;

(PITA) Posterior inferior temporal artery; (PoA) Parieto-occipital artery; and (SA) Splenial artery.



57

Anomalies of the PCA are uncommon; however a large fenestration was observed in the left P2A

segment in one case in the pilot study. This is illustrated in Figure 5.2. There were no cases of duplication

or triplication of the posterior cerebral artery.

Figure 5.2: Fenestration of the P2A segment.

The branching pattern of the PCA was assessed, since the literature does not give a sufficient description

on this subject. Monofurcation, bifurcation and trifurcation was described and these different branching

types are illustrated in the line diagram in Figure 5.3.


58

Figure 5.3: The different branching types of the posterior cerebral artery. A) Monofurcation; B)

Bifurcation; and C) Trifurcation. (CA) Calcarine artery; and (PoA) Parieto-occipital artery.

The literature states that the main branching of the PCA is at the division between the PoA and the

calcarine artery (end of the main trunk). In the 20 hemispheres that were assessed, this pattern was only

observed in one hemisphere. This branching type was referred to as “monofurcation” of the PCA (Fig.

5.3A).

In the other cases there was an additional branching before the division of the calcarine artery and PoA,

resulting in two similar sized trunks. This branching type was referred to as “bifurcation” of the PCA

(Fig. 5.3B). This bifurcation was observed at the origin of the CTA in six cases. When the common

temporal artery was absent, this bifurcation was located at the origin of the PITA in eight cases, and at

the origin of the MITA in two cases.

A “trifurcation” branching type (Fig. 5.3C) was observed in the remaining three hemispheres. The first

case was due to fenestration of the P2A segment (Fig. 5.3). In the second case there was early branching

of the parieto-occipital and calcarine artery with the MITA arising at the bifurcation. In the remaining

case the anterior and posterior inferior temporal arteries arose at the same origin, resulting in trifurcation.


59

5.4. PRESENT STUDY: ANTERIOR CEREBRAL ARTERY

In the present study a total of 121 hemispheres were studied to assess the anatomy of the ACA, including

60 right, and 61 left hemispheres. The segments, cortical branches and anomalies of the ACA are

described separately.

5.4.1. Segments

The diameter and length of the segments of the ACA were measured and is tabulated in Table 5.4. A

comparison is made between the left and right sides, sex, population groups and different age groups.

Few studies comment on these parameters.

There were statistically significant differences between the right and left A3 segment diameter and

length. There was also a statistically significant difference between the right and left A4 segment length.

The only statistically significant difference between males and females were in the A3 segment length

(females had a shorter A3 segment). The only statistically significant difference between population

groups were between Group 1 (specimens from the coloured population group) versus Group 3

(specimens from the white population group) for the A3 segment diameter (specimens from the white

population group had a larger diameter). There were no statistically significant differences observed

between the different age groups for the diameter and length of the A2, A3 and A4 segments. The

statistically significant differences are indicated in the table (Table 5.4).


60

Table 5.4: The average diameter (mm) and length (mm) of the A2, A3 and A4 segments observed bilaterally, between males and

females, different population groups and different age groups.

Segment Average Bilateral Sex Population Groups Age Groups

Right Left Male Female Group 1:

Coloured

Group 2:

Black

Group 3:

White

Group 1:

22-34

Group 2:

35-48

Group 3:

49-75

A2 D 2.3 2.3 2.4 2.4 2.3 2.3 2.4 2.7B 2.3 2.4 2.4

L 19.2 19.1 19.5 19.6 18.5 19.9 18.7 16.9B 19.2 19.5 18.8

A3 D 2.1 2.0* 2.2* 2.1 2.1 2.0 2.1 2.4 2.0 2.1 2.1

L 36.3 37.2* 35.7* 37.4* 34.2* 35.5 37.1 41.5 35.7 35.4 38.3

A4 D 1.6 1.6 1.7 1.7 1.6 1.7 1.6 1.6 1.6 1.7 1.6

L 25.4 26.1* 24.5* 25.8 24.0 25.2 26.3 23.0 24.9 26.4 24.7

(D) Diameter; (L) Length

(*) Indicates a statistically significant difference (p < 0.05)

(B) Indicates a statistically significant difference (p < 0.05) between Group 1 and Group 3



61

5.4.2. Cortical Branches

The diameter and length of the ACA cortical branches were measured. Any absence, duplications or

triplications were reported and the origins of the branches were noted.

5.4.2.1. Diameter and Length

The diameter and length of the different ACA cortical arteries are tabulated in Table 5.5. A comparison

is made between the left and right sides, sex, population groups and different age groups. Very few

studies commented on these parameters. The cortical branch with the greatest diameter was the

callosomarginal artery. The smallest arteries were the IfO and FpA (0.9 mm). The IfO also had the

shortest length (18.8 mm) and the parietal arteries had the longest length.

There were statistically significant differences between the length of the FpA, the anterior, middle and

posterior internal frontal arteries on the right and left side (left side usually larger). The diameter of the

FpA and internal frontal artery was bilaterally (between left and right) statistically significantly different.

The only statistically significant difference between males and females was the PLA length (longer in

males). There was no statistically significant difference between the different population groups. A

statistically significant difference was observed between different age groups in PIFA and PLA diameter.

The older groups (Group 2 and Group 3) had larger diameters compared to the younger group (Group

1). The IFA length was statistically significantly different between age Group 1 and Group 3 (older age

group had a longer length). The statistically significant differences are indicated in the table (Table 5.5).


62

Table 5.5: The average diameter (mm) and length (mm) of the anterior cerebral cortical branches observed bilaterally, between

males and females, different population groups and different age groups.

Cortical

Arteries

Average Bilateral Sex Population Groups Age Groups


Coloured

Group 2:

Black

Group 3:

White

Group 1:

22-34

Group 2:

35-48

Group 3:

49-75

IfO D 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.8 0.9 0.9 0.9

L 18.8 19.0 17.7 18.6 18.0 19.7 14.6 22.0 22.1 15.0 16.5

FpA D 0.9 0.9* 1.0* 1.0 0.9 0.9 0.9 1.1 0.9 1.0 1.0

L 20.1 22.4* 17.6* 19.2 22.1 21.8 16.9 14.5 19.5 19.5 20.8

IFA D 1.5 1.5* 1.6* 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.6

L 27.4 28.6 26.0 27.2 27.4 27.6 26.2 28.5 20.9 23.4 34.0B

AIFA D 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.2 1.0 1.1 1.1

L 28.6 30.9* 25.8* 27.8 30.2 28.7 28.2 26.3 27.9 28.4 28.4

MIFA D 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.1 1.2 1.2

L 41.1 43.3* 38.6* 41.8 39.0 41.5 38.4 45.9 43.5 37.1 42.8

PIFA D 1.3 1.3 1.3 1.3 1.2 1.3 1.2 1.5 1.1 1.4A 1.4B

L 52.8 55.4* 50.2* 54.1 49.9 53.1 51.8 54.2 52.3 52.5 53.5

PLA D 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.4 1.2 1.4A 1.3B

L 71.9 73.6 69.4 74.3* 64.8* 70.7 72.4 74.8 69.2 71.1 73.7

SIPA D 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.3 1.1 1.2 1.2

L 81.3 83.0 79.7 82.6 78.3 83.0 78.5 75.5 79.3 78.2 85.3

IIPA D 1.0 1.0 1.0 1.0 1.0 1.0 1.0 0.9 1.0 1.0 1.0

L 81.5 83.4 79.9 82.8 77.4 80.7 82.4 78.0 80.1 81.9 80.5

CmA D 2.0 2.0 2.1 2.0 1.9 1.9 2.0 - 2.0 1.8 2.0

L 21.6 19.3 25.1 21.7 21.3 24.1 21.4 - 20.8 21.1 30.0

(AIFA) Anterior internal frontal artery; (CmA) Callosomarginal artery; (D) Diameter; (FpA) Frontopolar artery; (IFA) Internal frontal

artery; (IfO) Infra-orbital artery; (IIPA) Inferior internal parietal artery; (L) Length; (MIFA) Middle internal frontal artery; (PIFA) Posterior

internal frontal artery; (PLA) Paracentral lobule artery; and (SIPA) Superior internal parietal artery.


(A) Indicates a statistically significant difference (p < 0.05) between Group 1 and Group 2




63

5.4.2.2. Absence, duplication and triplication

The most variable artery was the CmA, since it was present in only 15 cases (12.4%). The PLA is referred

to as the most consistent artery (always present), and was perceived in the present study as well. Most

frequently absent was the CmA and the IFA in 87.6% and 70.2% of cases, respectively. In the literature

the presence of these arteries are described as inconstant. There were only two arteries that were never

absent, the PIFA and the paracentral lobule artery. The most commonly duplicated artery was the

paracentral lobule artery in 31.4% of cases. The infra-orbital artery, frontopolar artery, IFA and

callosomarginal arteries were never duplicated. There were only two triplicated arteries, the paracentral

lobule artery in one case (0.8%), and the IIPA in one case (0.8%).

5.4.2.3. Origins

The origins of the ACA cortical branches are tabulated in Table 5.6. The most common origins of the

cortical branches are illustrated in Figure 5.4, although it should be mentioned that this specific

configuration was not observed in the present study.

Figure 5.4: The most common origins of the anterior cerebral cortical branches.

(AIFA) Anterior internal frontal artery; (FpA) Frontopolar artery; (IfO) Infra-orbital artery; (IIPA)

Inferior internal parietal artery; (MIFA) Middle internal frontal artery; (PLA) Paracentral lobule artery;

(PIFA) Posterior internal frontal artery; (PrcA) Pericallosal artery; and (SIPA) Superior internal

parietal artery.


64

Table 5.6: The presence, duplication, triplication and origin of the anterior cerebral cortical branches observed in the present study.

IfO FpA AIFA MIFA PIFA IFA PLA SIPA IIPA CmA

Presence 41.3% 60.3% 97.5% 99.2% 100% 29.8% 100% 97.5% 69.4% 12.4%

Duplicated - - 5.8% 12.4% 15.7% - 31.4% 5.0% 5.8% -

Triplicated - - - - - - 0.8% - 0.8% -

A1 Segment 2.0% - 0.8% - - - - - - -

A2 Segment 68.0% 68.5% 28.8% 5.2% - 22.2% - 0.8% - 33.3%

A3 Segment 2.0% 8.2% 40.0% 49.6% 53.6% 69.4% 16.8% 8.1% 2.2% 60.0%

A4 Segment - - - - 15.7% - 42.4% 26.6% 6.5% -

A5 Segment - - - - - - 24.8% 56.5% 41.3% -

CmA 2.0% 4.1% 4.8% 10.4% 12.9% 8.3% 8.7% - - -

IFA 2.0% 4.1% 16.0% 27.4% 15.0% - - - - -

MedACA - - - 0.7% 0.7% - 3.7% 7.3% 3.3% -

AcoA - - - - - - - - - 6.7%

FpA 12.0% - - - - - - - - -

AIFA 12.0% 11.0% - 1.5% - - - - - -

MIFA - 4.1% 9.6% - - - - - - -

PIFA - - - 5.2% - - 3.1% - - -

PLA - - - - 1.4% - - 0.8% - -

SIPA - - - - - - 0.6% - 2.2% -

PCA - - - - 0.7% - - - 44.6% -

(AcoA) Anterior communicating artery; (AIFA) Anterior internal frontal artery; (CmA) Callosomarginal artery; (FpA) Frontopolar artery;

(IFA) Internal frontal artery; (IfO) Infra-orbital artery; (IIPA) Inferior internal parietal artery; (MedACA) Median anterior cerebral artery;

(MIFA) Middle internal frontal artery; (PCA) Posterior cerebral artery; (PIFA) Posterior internal frontal artery; (PLA) Paracentral lobule

artery; (PoA) Parieto-occipital artery; and (SIPA) Superior internal parietal artery.



65

The IfO and frontopolar artery mostly originated from the A2 segment in 68.0% and 68.5% of cases,

respectively. The CmA, anterior, middle and posterior internal frontal arteries, and the IFA usually

originated from the A3 segment. The paracentral lobule artery typically originated from the A4 segment

and the SIPA from the A5 segment. The IIPA originated almost equally from the PCA and A5 segment

in 44.6% and 41.3%, respectively.

Uncommon origins included the IfO arising from the AIFA and FpA in 12.0% each, and the FpA arose

from the AIFA in 11.0% and from the MIFA in 9.6% of cases. The SIPA originated from the A2 segment

in one cases. This was due to the CmA that was present and gave origin to all the cortical branches except

the SIPA (the IIPA was absent).

The IfO and FpA commonly arose as common trunks in 11 cases. These common trunks originated from

the A2 segment (seven cases), AIFA (two cases), A3 segment (one case) and the callosomarginal artery

(one case). The frontopolar artery and AIFA arose as a common trunk in ten cases. These common trunks

originated from the A2 segment (eight cases), A3 segment (one case) and CmA (one case). In one case

the infra-orbital artery and AIFA originated from a common trunk from the A1 segment.

(i) Callosomarginal artery

The CmA was observed in only 15 cases (all typical configuration). The callosomarginal artery

originated from the AcoA in one case (6.7%), from the A2 segment in 33.3% and from the A3 segment

in 60.0% of cases in the present study. Furthermore, the CmA gave origin to the following subgroups

(Fig. 5.5): the middle and posterior internal frontal arteries and PLA (46.7%), the anterior, middle and

posterior internal frontal arteries and the PLA (20.0%), the IFA, posterior internal frontal artery and PLA

(20.0%), the frontal arteries and paracentral lobule and the FpA (6.7%), and the anterior and middle

internal frontal arteries, IfO and frontopolar artery.


66

Figure 5.5: The different configurations of the callosomarginal artery. (AIFA) Anterior internal

frontal artery; (FpA) Frontopolar artery; (IfO) Infra-orbital artery; (MIFA) Middle internal frontal

artery; (PLA) Paracentral lobule artery; and (PIFA) Posterior internal frontal artery.

(ii) Frontal arteries

The frontal arteries can originate from a common trunk, referred to as the internal frontal artery. The

IFA was present in 36 cases (29.8%) in the present study. The IFA gave origin to the anterior and middle

internal frontal arteries in 41.7%, to the middle and posterior internal frontal arteries in 44.4%, and to all

three frontal arteries in 13.9% of cases observed. These different configurations are illustrated in Figure

5.6.

Figure 5.6: The different configurations of the internal frontal artery. (AIFA) Anterior internal

frontal artery; (MIFA) Middle internal frontal artery; and (PIFA) Posterior internal frontal artery.


67

The diameter of the IFA was the smallest when giving origin to the anterior and middle internal frontal

arteries (1.4 mm) and largest when supplying all three frontal arteries (1.7 mm). The diameter was,

however, largest when the IFA originated from the A3 segment (1.6 mm).

5.4.3. Anomalies

The azygos ACA was not observed and no ACA fenestrations were observed in the present study. There

were seven cases (11.6%) of a median ACA (Fig. 5.7 and Fig. 5.8) and 12 cases (19.8%) of a

bihemispheric ACA observed in the present study (Fig. 5.9 and Fig. 5.10). Insufficient details regarding

the median and bihemispheric anterior cerebral arteries are given in the literature and these anomalies

are usually only mentioned. Little or no description is given on which branches are given off by these

abnormal arteries, or between which cortical arteries the bihemispheric branch arises.

5.4.3.1. Median anterior cerebral artery

The median ACA was observed in seven specimens and a line diagram of each case is given in Figure

5.7. The area supplied by the bihemispheric branch is indicated in green. The MedACA originated mostly

from the AcoA in 85.7% (six cases) and from the A2 segment in 14.3% (one case). Two subgroups can

be described, unilateral and bilateral MedACA.


68

Figure 5.7: The median anterior cerebral arteries observed in the present study.



(PIFA) Posterior internal frontal artery; and (SIPA) Superior internal parietal artery.

The median ACA supplied both hemispheres in four cases (bilateral median ACA) and only one

hemisphere in three cases (unilateral median ACA). The only arteries that arose from the MedACA were

the SIPA (most common), IIPA and paracentral lobule artery. The SIPA always originated from the

MedACA when present and in cases where both hemispheres where supplied by the MedACA, the

superior internal parietal artery arose from the MedACA to supply both hemispheres. The paracentral

lobule artery was present in six of the seven cases and the IIPA in only three cases.

(i) Unilateral median anterior cerebral artery

In the first case, the median ACA arose from the left A2 segment, although the MedACA only gave

origin to branches on the right (SIPA and paracentral lobule artery). In the second case, the MedACA

only gave rise to the SIPA. This case can be viewed as an anomalous origin of the SIPA from the AcoA.

In the third case, the median ACA only gave origin to the parietal arteries.


69

(ii) Bilateral median anterior cerebral artery

The remaining four cases were all bilateral, therefore supplying both hemispheres. In Case 4 and 6 (Fig.

5.7), the same arteries arose bilaterally (the SIPA and paracentral lobule artery in Case 4, and the SIPA

in Case 6) from the MedACA. The MedACA in Case 5 gave rise to two cortical branches on the left

(SIPA and paracentral lobule artery) and three on the right (PLA and parietal arteries). In Case 7 the

MedACA gave rise to the parietal arteries on the right, and the SIPA and paracentral lobule artery on the

left.

Figure 5.8: Median anterior cerebral artery.

5.4.3.2. Bihemispheric anterior cerebral artery

A bihemispheric ACA was observed in 19.8% in the present study and a line diagram of each case is

given in Figure 5.9. The cortical branches arising from the bihemispheric branch is indicated in red. The

bihemispheric branches originated between two paracentral lobule arteries in three cases, between the

MedACA


70

PLA and the PIFA in three cases, and between the anterior and middle internal frontal arteries in three

cases.

Figure 5.9: Bihemispheric anterior cerebral arteries observed in the present study.



(PIFA) Posterior internal frontal artery; and (SIPA) Superior internal parietal artery.

Excluding Case 5 and 9, the remaining 10 cases can be divided into two groups; one bihemispheric

branch from the right to the left hemisphere (three cases), and one bihemispheric branch from the left to

the right hemisphere (seven cases). When the bihemispheric branch gave rise to arteries from the left to

the right hemisphere, one to five cortical branches originated from the bihemispheric branch. When the


71

bihemispheric branch supplied arteries to the left side, two or three cortical branches originated from the

bihemispheric branch.

In Case 5 the bihemispheric branch gave rise to a branch supplying the ipsilateral as well as the

contralateral hemisphere. In Case 7 an anastomosis between the bihemispheric branch arising from the

right ACA (giving origin to the left IIPA and SIPA) and the left superior internal parietal artery was

observed. The diameter and length of this anastomosis was 0.9 mm and 2.0 mm, respectively. Case 8

was the only specimen where only one artery (IIPA) originated from the bihemispheric branch. This can

also be viewed as an anomalous origin of the IIPA from the contralateral ACA and was also the only

case where the SIPA did not originate from the bihemispheric branch. In Case 9 there were two

bihemispheric branches observed in one specimen. The first branch gave rise to the PLA and the second

branch to the parietal arteries. The most frequent cortical arteries arising from a bihemispheric branch

were the SIPA in 11 out of 12 cases, and the IIPA and paracentral lobule artery in eight cases each.


72

Figure 5.10: Bihemispheric anterior cerebral artery. A) Left hemisphere receiving branch from the

right; B) Bihemispheric branch from the right to the left hemisphere; and C) Superior view.

A

B

C


73

The diameter and length of the bihemispheric and median anterior cerebral arteries were measured and

the results are tabulated in Table 5.7. The diameters were measured at the origin of the BihemACA or

MedACA. The cortical arteries that originated from the bihemispheric ACA and MedACA are also

tabulated in Table 5.7. Length 1 refers to the distance of the origin of the artery (either BihemACA or

MedACA) from the AcoA. The MedACA arose from the A2 segment in only one case (Case 1), therefore

this was the only MedACA case with a measurement for Length 1. Length 2 refers to the length of the

crossing branch, and the length of the MedACA before division into cortical branches. This is illustrated

in Figure 5.11.

Figure 5.11: The measurements of the anomalies of the anterior cerebral artery.


74

Table 5.7: The diameter (mm), length (mm) and cortical arteries originating from the bihemispheric and median anterior cerebral

artery.

Case Variation Diameter Length 1 Length 2 Cortical Arteries

Right side Left side

Case 1 BihemACA 1.8 57.0 41.5 SIPA, IIPA -

Case 2 BihemACA 2.1 36.0 13.0 - PLA, PLA, SIPA

Case 3 BihemACA 1.8 32.5 8.0 PIFA, PLA, SIPA -

Case 4 BihemACA 1.8 42.7 25.0 PLA, SIPA -

Case 5 BihemACA 2.4 36.7 5.7 IIPA -

- 36.7 18.7 - MIFA, PIFA, PLA, SIPA

Case 6 BihemACA 2.2 40.0 33.0 PIFA, PLA, SIPA, IIPA -

Case 7 BihemACA 1.9 64.7 19.0 - SIPA, IIPA

Case 8 BihemACA 1.7 62.2 - IIPA -

Case 9 BihemACA

Branch 1: 1.1 63.0 - - PLA

Branch 2: 1.4 69.0 13.0 - SIPA, IIPA

Case 10 BihemACA 1.2 66.4 22.5 - SIPA, IIPA

Case 11 BihemACA 2.0 26.0 17.5 MIFA, PIFA, PLA, SIPA, IIPA -

Case 12 BihemACA 2.4 53.2 19.0 PLA, SIPA -

Case 1 MedACA 2.0 7.5 60.0 PLA, SIPA -

Case 2 MedACA 1.8 - - - SIPA

Case 3 MedACA 1.7 - 95.0 SIPA, IIPA -

Case 4 MedACA 1.7 - Right: 100.7 PLA, PLA -

Left: 102.7 - PLA, PLA

Case 5 MedACA 2.4 - Right: 75.7 IIPA, PLA, SIPA -

Left: 71.5 - PLA, SIPA

Case 6 MedACA 1.3 - 72.5 SIPA SIPA

Case 7 MedACA 1.9 - Right: 111.7 SIPA, IIPA -

Left: 105.9 - PLA, SIPA

(BihemACA) Bihemispheric anterior cerebral artery; (IIPA) Inferior internal parietal artery; (MedACA) Median anterior cerebral artery;

(MIFA) Middle internal frontal artery; (PIFA) Posterior internal frontal artery; (PLA) Paracentral lobule artery; and (SIPA) Superior internal

parietal artery.



75

The average diameter of both the BihemACA and MedACA was 1.8 mm. Branches supplying the right

side were larger, since the average diameter of bihemispheric branches on the right was 2.0 mm, and on

the left 1.5 mm. Both the unilateral and the bilateral MedACA had an average diameter of 1.8 mm. The

average distance of the origin of the BihemACA (Length 1) from the AcoA was 43.8 mm on the right,

and 56.0 mm on the left.

The MedACA and the BihemACA can have very similar definitions. The definition for the BihemACA

is the presence of a branch that supplies the contralateral hemisphere, where the ipsilateral ACA is

hypoplastic or terminates early. The definition for the MedACA is the presence of an additional branch

and the ACA or the A2 segments are still present and not hypoplastic. Additional classification is needed

for these anomalies. Figure 5.12 illustrates the extended criteria of the median ACA, bihemispheric ACA

and the unusual cortical artery.

Figure 5.12: Clarification on the median anterior cerebral artery, the bihemispheric anterior

cerebral artery, and unusual origin of a cortical artery.

If the abnormal artery originates proximal to the first cortical artery, it was considered a median ACA

(artery can supply one or both hemispheres, or only one cortical artery). However, if the abnormal artery

originates distal to the first cortical artery and supplies the contralateral hemisphere, it was considered a

bihemispheric branch. Furthermore, if the unusual artery originates distal to the first cortical artery and

supplies the ipsilateral hemisphere, it was considered a cortical artery with an abnormal origin.


76


77

5.5. PRESENT STUDY: MIDDLE CEREBRAL ARTERY

The present study consisted of 100 hemispheres to assess the anatomy of the MCA. This included 50

right, and 50 left hemispheres. The trunks, cortical branches, branching and anomalies of the MCA are


5.5.1. Trunks

The diameter of the M1 segment and trunks (superior, middle and inferior trunks) observed bilaterally,

between males and females, the different population groups and in different age groups are given in

Table 5.8. The diameter was measured at the origin. Few studies comment on these parameters.

The diameter of the M1 segment and the trunks (superior, middle and inferior trunks) had no statistically

significant differences between the right and left sides, or between males and females. There was a

statistically significant difference between the diameter of the M1 segment between the coloured and the

white population group. The larger diameter was observed in the specimens from the white population

group. There was also a statistically significant difference between the M1 segment diameter between

the different age groups (Group 1 versus Group 2, and Group 1 versus Group 3). A statistically

significant difference was found between the younger group and the older groups for the M1 diameter,

although there were no statistically significant differences observed in the superior, middle or inferior

trunks. The statistically significant differences are indicated in the table (Table 5.8).

The diameter and length of the M1 segment were measured by previous authors in similar studies112, 113,

123, 124, 128, 231-233 and this is tabulated in Table 5.9. The predivision length was measured from the origin

of the MCA to the main branching (end of main trunk).


78

Table 5.8: The average diameter (mm) of the M1 segment, superior, middle and inferior trunks observed bilaterally, between males

and females, different population groups and different age groups.

Trunks Average Bilateral Sex Population Groups Age Groups


Coloured

Group 2:

Black

Group 3:

White

Group 1:

22-34

Group 2:

35-48

Group 3:

49-75

M1 D 2.9 2.9 2.9 2.9 2.8 2.8 2.9 3.4B 2.7 2.9A 3.0B

SUP D 2.2 2.2 2.2 2.2 2.1 2.1 2.3 2.3 2.1 2.2 2.3

MID D 2.0 1.9 2.0 2.0 1.7 1.9 1.8 2.3 2.0 1.7 2.0

INF D 2.0 2.1 2.0 2.0 2.0 2.0 2.1 2.3 1.9 2.0 2.1

(D) Diameter; (INF) Inferior trunk; (MID) Middle trunk; and (SUP) Superior trunk.



Table 5.9: The diameter (mm) of the M1 segment and predivision length (mm)112, 113, 123, 124, 128, 231-233.

Grellier

et al.

(1978)

van der

Zwan et al.

(1993)

Meneses

et al.

(1997)

Türe

et al.

(2000)

Idowu

et al.

(2002)

Tarasów

et al.

(2007)

Vuillier

et al.

(2008)

Zurada

et al.

(2011)

Sadatom

o et al.

(2013)

Present

Study

R Diameter 4.1

2.8 3.2 3.2 3.5

2.4 3.4

- 2.2 2.9

L Diameter 2.7 2.5 - 2.2 2.9

R Predivision length 16.6

- 18.5 23.4 15.4

14.5 13.0

15.5 - 19.7

L Predivision length - 13.8 15.7 - 20.9

(L) Left; (R) Right.



79

The predivision length observed in the present study was similar to the results of Meneses et al.123 and

Türe et al.112. The M1 segment diameter was similar to the results of van der Zwan et al.231, Meneses et

al.123 and Türe et al.112. Not all authors give separate results for the right and left sides.


There is still controversy on the most common course and origin of MCA branches111. The cortical

branches of the MCA can arise as early branches, or from the superior, inferior or middle trunk. The size

and the length of these cortical branches can vary, and very few studies comment on these aspects.

5.5.2.1. Diameter and length

The diameter and lengths of the MCA cortical branches are tabulated in Table 5.10. A comparison is

made between the right and left, males and females, different population groups and different age groups.

The arteries with the greatest diameter were the PPA and angular arteries. The smallest artery was the

TpA (0.9 mm). The TpA was also the shortest (25.1 mm) and the angular artery the longest (93.7 mm).

The angular artery can be seen as the terminal branch of the MCA.

Bilaterally there was a statistically significant difference in the diameter of the OfA and calcarine artery,

and the length of the PPA. The length of the APA was the only statistically significant difference between

males and females; males had a statistically significantly longer length. The diameter of the CTA was

the only statistically significant difference between the population groups. Specimens from the white

population group had a statistically significantly larger diameter compared to that of the coloured

population group (1.6 mm and 1.3 mm, respectively). The diameter of the PPA was statistically

significantly different between the different age groups (Group 1 versus Group 2, and Group 1 versus

Group 3). The older groups (1.5 mm) had a statistically significantly larger diameter compared to the

younger age group (1.3 mm). The length of the PfA, common temporal artery and the PTA was

statistically significantly different between the younger and oldest age group (Group 1 versus Group 3).

The length of the ToA was statistically significantly different between the younger (Group 1) and the

older age group (Group 2). The statistically significant differences are indicated in the table (Table 5.10).


80

Table 5.10: The average diameter (mm) and length (mm) of the middle cerebral cortical branches observed bilaterally, between


Cortical

Arteries



Coloured

Group 2:

Black

Group 3:

White

Group 1:

22-34

Group 2:

35-48

Group 3:

49-75

OfA D 1.2 1.16* 1.24* 1.2 1.2 1.2 1.3 1.2 1.2 1.2 1.2

L 37.8 40.3 35.2 37.0 39.3 37.0 37.3 48.2 35.7 36.2 40.7

PfA D 1.3 1.3 1.3 1.3 1.2 1.2 1.3 1.4 1.2 1.3 1.3

L 47.1 49.0 45.2 47.1 47.1 46.7 46.0 56.0 41.5 48.2 51.9B

PcA D 1.3 1.3 1.3 1.3 1.4 1.3 1.3 1.3 1.2 1.3 1.3

L 50.7 50.8 50.6 52.7 46.5 50.8 50.9 52.6 50.7 49.7 53.9

CA D 1.3 1.3* 1.4* 1.3 1.3 1.3 1.4 1.3 1.2 1.4 1.4

L 50.7 51.6 49.8 51.6 49.0 50.3 51.2 47.3 55.0 47.7 48.8

APA D 1.3 1.3 1.4 1.3 1.4 1.3 1.3 1.4 1.3 1.3 1.3

L 67.1 66.5 67.8 70.1* 60.3* 64.4 71.2 73.0 69.3 71.7 62.5

PPA D 1.4 1.5 1.4 1.5 1.4 1.4 1.4 1.7 1.3 1.5A 1.5B

L 80.7 74.6* 86.8* 80.4 81.6 83.2 76.5 85.9 80.9 73.4 83.4

AA D 1.4 1.4 1.4 1.4 1.4 1.4 1.5 1.4 1.4 1.4 1.4

L 93.9 89.9 98.0 91.8 97.6 95.9 93.9 79.8 93.3 102.2 84.5

ToA D 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.5 1.2 1.3 1.4

L 89.9 84.5 95.4 91.2 87.4 86.8 98.0 80.0 82.0 108.3A 81.5

CTA D 1.3 1.3 1.4 1.3 1.4 1.3 1.4 1.6B 1.3 1.4 1.3

L 25.4 25.7 25.1 27.7 21.1 25.5 25.1 26.5 19.8 24.9 32.1B

TpA D 0.9 0.9 0.9 0.9 1.0 0.9 0.9 0.9 0.9 0.9 0.9

L 25.1 25.6 24.6 24.3 26.8 27.2 23.8 20.6 25.5 26.2 25.3

ATA D 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0

L 39.2 39.8 38.6 39.6 38.4 38.4 41.1 40.8 37.2 41.2 40.6

MTA D 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.2 1.0 1.0 1.0

L 54.9 54.2 55.7 57.6 49.0 53.2 55.5 62.0 52.9 55.6 55.7

PTA D 1.1 1.1 1.1 1.1 1.1 1.0 1.1 1.1 1.1 1.0 1.0

L 79.1 74.5 83.7 78.4 81.1 84.7 68.3 85.2 73.2 69.8 93.6B

(AA) Angular artery; (APA) Anterior parietal artery; (ATA) Anterior temporal artery; (CA) Central artery; (CTA) Common temporal; (D)

Diameter; (L) Length; (MTA) Middle temporal artery; (OfA) Orbitofrontal artery; (PcA) Precentral artery; (PfA) Prefrontal artery; (PPA)

Posterior parietal artery; (PTA) Posterior temporal artery; (ToA) Temporooccipital artery; and (TpA) Temporopolar artery






81


The most consistent artery was the PfA, since it was always present and never duplicated or triplicated.

The CTA was the most commonly absent artery in 51.0% of cases. The most duplicated arteries were

the APA in 9.0% and the central artery in 8.0% of cases. The only triplicated arteries were the central

and angular arteries in one case each.

5.5.2.3. Origins

For the description of the origins, the middle trunk was only described in the true trifurcation cases and

not for proximal and lateral trifurcation. There were only six hemispheres that had a true trifurcation. In

the other cases the cortical branches originated from either the superior trunk, inferior trunk, or as an

early branch (Table 5.11). The MCA cortical branches can be described in three groups; the frontal

branches, the parietal branches, and the temporal branches. The origins of the MCA cortical branches

are tabulated in Table 5.11. The most common origins of the cortical branches are illustrated in Figure

5.13.

Figure 5.13: The most common origins of the middle cerebral cortical branches.


artery; (CTA) Common temporal; (MTA) Middle temporal artery; (OfA) Orbitofrontal artery; (PcA)

Precentral artery; (PfA) Prefrontal artery; (PPA) Posterior parietal artery; (PTA) Posterior temporal

artery; (ToA) Temporooccipital artery; and (TpA) Temporopolar artery


82

Table 5.11: The presence, duplication, triplication and origin of the middle cerebral cortical branches observed in the present study.

OfA PfA PcA CA APA PPA AA CTA TpA ATA MTA PTA ToA

Presence 99.0% 100% 99.0% 100% 100% 100% 97.0% 49.0% 90.0% 97.0% 94.0% 82.0% 95.0%

Duplicated 5.0% - 2.0% 8.0% 9.0% 3.0% 5.0% - 1.0% 1.0% 3.0% - -

Triplicated - - - 1.0% - - 1.0% - - - - - -

EB 24.0% 21.0% 12.9% 3.7% - - - 44.9% 53.8% 26.5% 4.1% - 1.1%

INF - - - 12.8% 34.9% 53.4% 76.7% 53.1% 20.9% 27.6% 36.1% 69.5% 91.6%

SUP 66.4% 79.0% 82.2% 78.9% 58.7% 42.7% 22.3% - - - - - 5.3%

MID - - 1.0% 2.7% 5.5% 2.9% 1.0% - - - - - -

CTA - - - - - - - - 22.0% 40.8% 51.5% 19.5% 1.1%

PfA 9.6% - 2.0% - - - - - - - - - -

CA - - 2.0% - 0.9% - - - - - - - -

APA - - - 2.7% - - - - - - - - -

AA - - - - - 1.0% - - - - - - -

ATA - - - - - - - - 2.2% - - - -

MTA - - - - - - - - 1.1% 4.1% - 1.2% 1.1%

PTA - - - - - - - - - 1.0% 4.1% - -

ToA - - - - - - - 2.0% - - 4.1% 9.8% -

The diameter and length are given in millimetres (mm). (AA) Angular artery; (APA) Anterior parietal artery; (ATA) Anterior temporal

artery; (CA) Central artery; (CTA) Common temporal; (EB) Early branch; (INF) Inferior trunk; (MID) Middle trunk; (MTA) Middle

temporal artery; (OfA) Orbitofrontal artery; (PcA) Precentral artery; (PfA) Prefrontal artery; (PPA) Posterior parietal artery (PTA) Posterior

temporal artery; (SUP) Superior trunk; (ToA) Temporooccipital artery; and (TpA) Temporopolar artery.



83

(i) The frontal branches

The OfA and prefrontal arteries frequently arose from the superior trunk in 66.4% and 79.0% of cases,

respectively. The precentral and central arteries frequently arose from the superior trunk in 82.2% and

78.9%, respectively. Uncommon origins included the orbitofrontal artery arising from the PfA in 10

cases, and the central artery arising from the APA in three cases. The PcA originated from the prefrontal

artery in two cases, and from the central artery in two cases.

(ii) The parietal branches

The APA most commonly originated from the superior trunk in 58.7% and origin from the inferior trunk

was also frequent (34.9%). The posterior parietal artery and the angular artery usually branched from the

inferior trunk in 53.4% and 76.7%, respectively, and from the superior trunk in 42.7% and 22.3%,

respectively. Uncommon origins included the APA arising from the central artery in one case and the

PPA arising from the angular artery in one case.

Common trunks were observed between the OfA and prefrontal artery in 19 cases and between the

prefrontal artery and the PcA in 11 cases. The central and precentral artery had a common trunk in seven

cases and the central artery and APA arose as a common trunk in two cases. In 76.9% the common trunks

arose as an early frontal branch, and in 23.1% the trunks arose from the superior trunk.

(iii) The temporal and temporo-occipital branches

The temporal arteries usually originated either as early temporal branches, or from the inferior trunk.

The anterior, middle and posterior temporal arteries could also originate from the common temporal

artery. The temporopolar artery usually originated as an early temporal branch (53.8%). The anterior and

middle temporal arteries usually originated from the common temporal artery in 40.8% and 51.5%,

respectively. The ToA, PTA and common temporal artery frequently originated from the inferior trunk

in 91.6%, 69.5% and 53.1% of cases, respectively. A common trunk between the temporopolar artery

and ATA was observed in 25 cases, originating from either the inferior trunk (five cases) or as an early

temporal branch (20 cases).

The common temporal artery was present in 49.0% of cases and there are three different configurations

that can be observed. The CTA can give rise to the anterior and middle temporal arteries (67.3%), the

middle and posterior temporal arteries (20.4%), or it can give rise to all three temporal arteries (12.2%).


84

The temporopolar artery can also originate from the CTA and this was observed in 20 cases. Table 5.12

and Figure 5.14 illustrate the 12 configurations of the temporal arteries. Cases with duplication or

absence of the temporal arteries were excluded and only 33 cases remained.

Table 5.12: Configuration of the superior temporal arteries.

Type CTA

Origin

TpA Origin ATA

Origin

MTA Origin PTA Origin n=33 Cases

1 ETB CTA CTA CTA INF 27.3% 9

2 ETB ETB CTA CTA INF 9.1% 3

3 ETB ETB CTA CTA CTA 3.0% 1

4 ETB ETB* ETB* CTA CTA 3.0% 1

5 INF CTA CTA CTA CTA 9.1% 3

6 INF INF CTA CTA CTA 3.0% 1

7 INF CTA CTA CTA INF 12.1% 4

8 INF ETB CTA CTA INF 9.1% 3

9 INF INF CTA CTA INF 3.0% 1

10 INF ATA CTA CTA INF 3.0% 1

11 INF ETB* ETB* CTA CTA 12.1% 4

12 INF INF* INF* CTA CTA 6.1% 2

(ATA) Anterior temporal artery; (CTA) Common temporal; (ETB) Early temporal branch; (INF)

Inferior trunk; (MTA) Middle temporal artery; (PTA) Posterior temporal artery; and (TpA)

Temporopolar artery.

(*) Indicates a common trunk

The most common configuration was Type 1. In type 9, the common temporal artery originates as an

early temporal branch, and gives rise to the ATA, MTA and temporopolar artery. The PTA originates

from the inferior trunk and this was observed in nine cases.


85

Figure 5.14: Configuration of the superior temporal arteries. (ATA) Anterior temporal artery;

(MTA) Middle temporal artery; (PTA) Posterior temporal artery; and (TpA) Temporopolar artery.

5.5.2.4. Early branches

Early temporal branches were observed in 81.0%, and early frontal branches in 28.0% of cases. Both

early temporal and early frontal branches were observed in 24.0% of cases. There were only 15 cases

with no early branches in the present study.

5.5.3. Branching

In the case of bifurcation, the superior trunk usually gave origin to the OfA, PfA, precentral, and the

central arteries. The parietal and angular arteries originated from either the superior or the inferior trunks.

The inferior trunk gave origin to the temporal and temporo-occipital arteries.

True trifurcation was only observed in six cases and line diagrams of these cases are demonstrated in

Figure 5.15. When trifurcation was observed, the superior trunk usually gave origin to the OfA, PfA and

precentral arteries. The middle branch gave origin to the central artery (three cases), APA (five cases)

and PPA (three cases). The PcA and angular arteries originated from the middle trunk in one case each.

The inferior trunk usually gave origin to the temporal and temporo-occipital arteries. This is in

accordance with what is described in the literature.


86

Figure 5.15: The six cases of true trifurcation of the middle cerebral artery.


artery; (CTA) Common temporal artery; (MTA) Middle temporal artery; (OfA) Orbitofrontal artery;

(PcA) Precentral artery; (PfA) Prefontal artery; (PPA) Posterior parietal artery; (PTA) Posterior

temporal artery; (ToA) Temporooccipital artery; and (TpA) Temporopolar artery.

The different branching patterns were grouped into 11 different types (Fig. 2.6) and the results are

tabulated in Table 5.13. The branching subtypes were compared bilaterally, between males and females,

different population groups and different age groups. There were no cases of monofurcation,

pseudotrifurcation, tetrafurcation or pseudotetrafurcation observed in the present study. The most

common branching pattern was medial bifurcation in 34.0% of cases. Most authors only mention

bifurcation and trifurcation and do not elaborate on the different subtypes.


87

Table 5.13: The prevalence of the MCA branching observed bilaterally, between males and females, different population groups and

in different age groups.

Total Bilateral Sex Population group Age


Coloured

Group 2:

Black

Group

3: White

Unknown Group

1: 22-34

Group 2:

35-48

Group 3:

49-75

Unknown

True Trif. 6.0% 2.0% 4.0% 5.0% 1.0% 3.0% 1.0% 2.0% - - 1.0% 4.0% 1.0%

Proximal Trif. 9.0% 4.0% 5.0% 5.0% 4.0% 6.0% 1.0% - 2.0% 3.0% 1.0% 3.0% 2.0%

Distal Trif. 9.0% 4.0% 5.0% 8.0% 1.0% 5.0% 3.0% 1.0% - 4.0% 1.0% 4.0% -

Medial Bif. 34.0% 21.0% 13.0% 18.0% 16.0% 21.0% 8.0% 5.0% - 10.0% 9.0% 11.0% 4.0%

Lateral Bif. 22.0% 12.0% 10.0% 17.0% 5.0% 11.0% 11.0% - - 8.0% 9.0% 4.0% 1.0%

Medial pseudobif. 10.0% 4.0% 6.0% 10.0% - 3.0% 7.0% - - 1.0% 5.0% 3.0% 1.0%

Lateral pseudobif. 9.0% 2.0% 7.0% 5.0% 4.0% 6.0% 3.0% - - 2.0% 3.0% 3.0% 1.0%

Early Bif. 1.0% 1.0% - - 1.0% 1.0% - - - - - 1.0% -

(Bif) Bifurcation; (Trif) Trifurcation.



88

Bifurcation was observed in 75 cases, and these cases were further divided into medial bifurcation

(34.0%), lateral bifurcation (22.0%), medial pseudobifurcation (10.0%) and lateral pseudobifurcation

(9.0%). True trifurcation was observed in six cases only, proximal trifurcation in nine cases and distal

trifurcation in nine cases. A digital image of each of these branching types is given in Figure 5.16. There

was a statistically significant difference (p <0.05) between the branching subtypes between males (n=68)

and females (n=32). Males had more distal trifurcation, lateral bifurcations and medial

pseudobifurcation.


89

Figure 5.16: The middle cerebral artery branching subtypes. A) Proximal trifurcation; B) Distal

trifurcation; C) True trifurcation; D) Medial bifurcation; E) Lateral bifurcation; F) Medial

pseudobifurcation; and G) Lateral pseudobifurcation.

A

B

C

D

E

F

G


90

5.5.4. Anomalies

No cases of a duplicated MCA, accessory MCA or fenestration of the middle cerebral artery were

observed in the present study. True anomalies of the middle cerebral artery are very rare, especially in

comparison to anomalies in the anterior and posterior cerebral arteries.


91

5.2. PRESENT STUDY: POSTERIOR CEREBRAL ARTERY

The present study consisted of 124 hemispheres to assess the anatomy of the PCA. This included 62

right and 62 left hemispheres. The segments, cortical branches, branching and anomalies of the PCA are


5.2.1. Segments

The diameter and lengths of the PCA segments were measured and are tabulated in Table 5.14. A

comparison is made between the right and left sides, males and females, different population groups and

different age groups. Very few studies have measured the diameter and lengths of the PCA segments9,

200.

The only bilateral statistically significant difference was the diameter of the P2P segment (larger on the

left). The only statistically significant difference between males and females was the length of the P3

segment (longer in males). The diameter of the PCA segments and the length of the P3 segment, were

statistically significantly different in the different population groups (Group 1 versus Group 3). The P3

segment in specimens from the white population group (Group 3) had larger diameters, and a longer

length. There was a statistically significant difference between the different age groups in the diameter

of all three segments, and between the lengths of the P2A and P2P segments. The older groups had a

larger diameter and a longer length compared to the younger age group. There were no statistically

significant differences between Group 2 and Group 3 in either the population groups or between the age

groups. The statistically significant differences are indicated in the Table (Table 5.14).


92

Table 5.14: The average diameter (mm) and length (mm) of the P2A, P2P and P3 segments observed bilaterally, between males and

females, different population groups and different age groups.

Segments Average Bilateral Sex Population Groups Age Groups


Coloured

Group 2:

Black

Group 3:

White

Group 1:

22-34

Group 2:

35-48

Group 3:

49-84

P2A D 2.2 2.3 2.2 2.3 2.2 2.2 2.3 2.6B 2.0 2.2A 2.3B

L 39.0 39.7 38.3 39.8 37.2 38.4 39.5 39.8 36.3 39.7 40.7B

P2P

D 1.5 1.5* 1.6* 1.5 1.5 1.5 1.6 1.8B 1.4 1.5 1.6B

L 13.4 13.9 13.0 13.6 13.1 13.4 13.8 13.2 12.2 13.4 14.7B

P3 D 1.3 1.3 1.4 1.4 1.3 1.3 1.4 1.6B 1.2 1.4A 1.4B

L 23.1 22.7 23.6 23.9* 21.4* 22.0 23.8 29.0B 22.7 23.8 22.3

(D) Diameter; (L) Length.






93


The diameter and length of the PCA cortical branches were measured. Any absence, duplication or

triplications were reported and the origins of the branches were noted. Few studies have noted these

aspects.

5.2.2.1. Diameter and Length

The diameter and lengths of the PCA cortical branches were measured and are tabulated in Table 5.15.

A comparison is made between the right and left, males and females, different population groups and

different age groups. Very few studies have measured the diameter and lengths of the PCA cortical

branches88. The arteries with the greatest diameter were the CTA (1.5 mm) and PoA (1.3 mm). The

smallest artery was the SA (0.8 mm), and the calcarine artery and PoA were the longest (93.7 mm).

The length of the AITA and the diameter of the PoA were bilaterally statistically significantly different.

The diameter of the CTA was statistically significantly larger in males, and the length of the CA and

PoA was statistically significantly longer in males. The diameter of the CTA was statistically

significantly larger in Group 2 (specimens from the black population group) and Group 3 (specimens

from the white population group) compared to the coloured population group (Group 1). The diameter

of the SA was statistically significantly larger in the white population group (Group 3) compared to the

other population groups. The lengths of the CA and PoA were statistically significantly longer in the

white population group compared to the other population groups. There was a statistically significant

difference between the diameters of the CTA and PoA in comparison between the older age groups

(Group 2 and Group 3) and the youngest age group (Group 1). The length of the CTA was statistically

significantly longer in Group 2, compared to the youngest age group. There were no statistically

significant differences between Group 2 and Group 3 in either the population groups or between the age

groups. The statistically significant differences are indicated in the table (Table 5.15).


94

Table 5.15: The average diameter (mm) and length (mm) of the posterior cerebral cortical branches observed bilaterally, between


Cortical

Arteries



Coloured

Group 2:

Black

Group 3:

White

Group 1:

22-34

Group 2:

35-48

Group 3:

49-84

CTA D 1.5 1.5 1.5 1.6* 1.3* 1.3 1.7A 1.9B 1.2 1.7A 1.6B

L 26.2 27.0 25.4 27.7 22.7 25.2 26.3 30.3 21.6 28.5A 27.3

AITA D 0.9 0.9 0.9 0.9 0.8 0.9 0.9 0.9 0.8 0.9 0.9

L 24.8 27.0* 22.4* 25.0 24.0 23.9 26.3 24.4 25.7 24.1 24.4

MITA D 1.1 1.0 1.1 1.1 1.0 1.0 1.1 1.0 1.0 1.1 1.0

L 34.1 36.1 32.1 34.6 32.6 32.9 35.7 35.6 31.7 34.2 34.3

PITA D 1.2 1.3 1.2 1.3 1.2 1.2 1.3 1.3 1.2 1.3 1.2

L 36.6 37.5 35.4 37.4 34.3 34.8 37.9 40.9 34.4 35.8 36.8

CA D 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.2 1.1 1.1 1.1

L 54.0 53.2 54.8 57.0* 47.0* 51.9 54.7 64.9B 52.3 52.1 56.8

PoA D 1.3 1.26* 1.34* 1.3 1.3 1.3 1.3 1.5 1.2 1.3A 1.3B

L 53.8 52.9 54.7 57.1* 46.3* 51.9 54.3 64.9B 51.4 52.9 56.5

SA D 0.8 0.8 0.8 0.8 0.8 0.8 0.8 1.1B 0.8 0.8 0.9

L 51.6 52.1 51.1 50.8 53.5 51.4 52.8 53.2 47.4 59.2 50.4

(AITA) Anterior inferior temporal artery; (CA) Calcarine artery; (CTA) Common temporal artery; (D) Diameter; (L) Length; (MITA) Middle

inferior temporal artery; (PITA) Posterior inferior temporal artery; (PoA) Parieto-occipital artery; and (SA) Splenial artery.






95


The calcarine and parieto-occipital arteries were the most consistent, since these cortical branches were

observed in all hemispheres and were each only duplicated once. Most commonly absent was the

common temporal artery in 72.6%, and the splenial artery in 63.7% of cases. The anterior and posterior

inferior temporal arteries were typically duplicated, both in 10.5% of specimens. The AITA and PITA

was also the only arteries to be triplicated (Fig. 5.17). This was observed in three cases (2.4%) and one

case (0.8%), respectively.

Figure 5.17: Triplicated anterior inferior temporal artery (arrows indicate the three arteries).

(AITA) Anterior inferior temporal artery; (MITA) Middle inferior temporal artery; and (PITA)

Posterior inferior temporal artery.

5.2.2.3. Origins

The origins of the PCA cortical branches are tabulated in Table 5.16. The common temporal artery

originated from the P2A segment in all 34 cases (100%) and the temporal arteries most commonly

originated from the P2A segment. The PoA and the calcarine artery typically originated from the P3

segment, whereas the splenial artery usually originated from the PoA (20 cases).

AITA

PITA

MITA


96

Table 5.16: The presence, duplication, triplication and origin of the posterior cerebral cortical branches observed in the present

study.

CTA AITA MITA PITA CA PoA SA

Presence 27.4% 96.0% 91.9% 99.2% 100% 100% 36.3%

Duplicated - 10.5% 3.2% 10.5% 0.8% 0.8% -

Triplicated - 2.4% - 0.8% - - -

P2A Segment 100% 63.2% 50.0% 62.0% 12.0% 13.6% 17.8%

P2P Segment - - 0.8% 10.2% 20.0% 20.0% 8.9%

P3 Segment - - - 2.2% 65.6% 64.8% 15.6%

P4 Segment - - - - 0.8% 0.8% -

CTA - 21.3% 29.7% 19.0% - - -

AITA - - 1.7% - - - -

MITA - 6.6% - 0.7% - - -

PITA - 8.1% 16.1% - 1.6% - 4.4%

PoA - - - 1.5% - - 44.4%

CA - 0.7% 1.7% 4.4% - 0.8% 8.9%

(AITA) Anterior inferior temporal artery; (CA) Calcarine artery; (CTA) Common temporal artery; (MITA) Middle inferior temporal artery;

(PITA) Posterior inferior temporal artery; (PoA) Parieto-occipital artery; and (SA) Splenial artery.



97

Unusual origins included the anterior inferior temporal artery arising from the PITA in 11 cases (8.1%),

and from the MITA in nine cases (6.6%). The middle inferior temporal artery arose from the PITA in 19

cases (16.1%), and the PITA arose from the calcarine artery in six cases (4.4%). Unusual origins of the

PoA included an origin from the calcarine artery in one case (0.8%) and the calcarine artery arising from

the PITA in two cases (1.6%).

A common temporal artery was present in 34 cases. A common trunk typically bifurcates at almost a 90

degree angle and the cortical branches have similar diameters. The CTA can be absent, supply all three

temporal arteries, or only supply two temporal arteries. The common temporal artery gave origin to all

three inferior temporal arteries in 44.1%, to the anterior and middle inferior temporal arteries in 14.7%,

and to the middle and posterior inferior temporal arteries in 41.2%.

This study proposes a revised classification of the inferior temporal arteries, which excludes the

hippocampal arteries, and takes into account the origins of the inferior temporal cortical branches of the

PCA. The configuration of the temporal arteries was divided into 16 types according to the different

origins (illustrated in Figure 5.18). Cases with duplication, triplication or absent temporal arteries were

excluded and 84 cases remained. The configuration of the temporal arteries, with and without the CTA

is tabulated in Table 5.17 and illustrations are given (Fig. 5.18).


98

Table 5.17: Configuration of the inferior temporal arteries.

Type CTA AITA Origin MITA Origin PITA Origin n=84 Cases

1 Yes CTA CTA CTA 7.1% 6

2 Yes CTA CTA P2A Segment 7.1% 6

3 Yes P2A Segment CTA CTA 14.3% 12

4 Yes MITA CTA CTA 1.2% 1

5 No P2A Segment P2A Segment P2A Segment 32.1% 27

6 No P2A Segment PITA P2A Segment 9.5% 8

7 No MITA P2A Segment P2A Segment 6.0% 5

8 No P2A Segment P2A Segment P2P Segment 4.8% 4

9 No PITA PITA P2A Segment 4.8% 4

10 No P2A Segment P2A Segment Calcarine artery 3.6% 3

11 No MITA P2A Segment P2P Segment 2.4% 2

12 No P2A Segment AITA P2A Segment 2.4% 2

13 No P2A Segment P2P Segment P2P Segment 1.2% 1

14 No P2A Segment P2A Segment MITA 1.2% 1

15 No P2A Segment Calcarine artery Calcarine artery 1.2% 1

16 No Calcarine artery Calcarine artery Calcarine artery 1.2% 1

(AITA) Anterior inferior temporal artery; (CTA) Common temporal artery; (MITA) Middle inferior

temporal artery; and (PITA) Posterior inferior temporal artery.

When the CTA was present, the most common configuration was Type 3 (MITA and PITA arise from

common temporal artery, anterior inferior temporal artery from the P2A segment) in 12 cases (14.3%).

Type 5 (all three inferior temporal branches arise from P2A segment) was the most common

configuration in 27 of 84 cases (32.1%). These 16 types do not describe all possible configurations, only

the configurations observed in the present study.


99

Figure 5.18: Configuration of the inferior temporal arteries.

(AITA) Anterior inferior temporal artery; (CA) Calcarine artery; (MITA) Middle inferior temporal

artery; and (PITA) Posterior inferior temporal artery.


100

5.2.3. Branching

Three branching patterns of the distal PCA have previously been described by Milisavljević et al.197. In

Type 1 the terminal division is at the P3 or P4 segment. In Type 2 the terminal division is at the P3 or

P4 segment with the common temporal artery present. In Type 3 the terminal division is at the P2

segment. In the present study, Type 1, Type 2 and Type 3 were observed in 61 cases (50.0%), 21 cases

(17.2%), and 40 cases (32.8%), respectively. Two hemispheres were excluded where a terminal division

was not observed. In both cases the calcarine artery originated from the PITA. Therefore only 122

hemispheres were used for this analysis. These three branching types were further classified into seven

subtypes (Table 5.18).

Table 5.18: The branching subtypes of the posterior cerebral artery.

Type Terminal division point CTA Present Cases Total (n=122) Percentage

Type 1 P3 Segment No 61 61 Cases 50.0%

Type 2 P3 Segment Yes 20 21 Cases 17.2%

P4 Segment Yes 1

Type 3 P2A Segment No 12 40 Cases 32.8%

P2A Segment Yes 3

P2P Segment No 16

P2P Segment Yes 9

Type 2, as described by Milisavljević et al.197, was classified into two subtypes, terminal division at the

P3 segment, and terminal division at the P4 segment. Type 3 was classified into four subtypes, depending

on the origin (P2A or P2P segment) of the terminal division and the presence of the CTA. The prevalence

of these subtypes is tabulated in Table 5.18. Type 3 can be viewed as early branching, and this is

illustrated in Figure 5.19.


101

Figure 5.19: Early branching of the posterior cerebral artery (arrow indicates branching point).

(CA) Calcarine artery; and (PoA) Parieto-occipital artery.

As described in the pilot study (section 5.3 pp. 57, 58), the PCA branching can be classified into

monofurcation, bifurcation and trifurcation. This should not be confused with duplication or triplication

of the PCA. When monofurcation is present there is no branching before the origin of the PoA and

calcarine artery. This is the typical configuration described in the literature (the normal branching

pattern). This was observed in only 34 cases (27.4%) in the present study.

In bifurcation there is an additional branching before the origin of the calcarine artery and PoA. The

bifurcation branching type was observed in 84 cases (67.7%) in the present study. The bifurcation was

due to the origin of the PITA in 52 cases, the origin of the common temporal artery in 25 cases, and the

origin of the MITA in seven cases. In trifurcation there is also additional branching (three trunks) before

the origin of the calcarine artery and PoA. The trifurcation branching type was observed in six cases

(4.8%) in the present study. This was due to origin of the PITA and MITA (three cases) at the same

place, or origin of the PITA and calcarine artery (three cases). An example of monofurcation, bifurcation

and trifurcation type is given in Figure 5.20.

PoA

CA


102

Figure 5.20: The branching patterns of the posterior cerebral artery. A) Monofurcation; B)

Bifurcation; and C) Trifurcation (arrows indicate branching points). (CA) Calcarine artery; (PITA) Posterior inferior temporal artery; and (PoA) Parieto-occipital artery.

A

B

C

CA

PITA

PoA

PITA

PoA

CA

PoA

CA


103

5.2.4. Anomalies

Duplication or triplication of the PCA was not observed in the present study; however, there were two

cases (1.6%) of fenestration of the P2A segment. These two cases are illustrated in Figure 5.21.

Figure 5.21: Fenestration of the right (A) and left (B) posterior cerebral artery (arrow indicates

fenestration).

A

B


104

This first fenestration case (Fig. 5.21A) was similar to the case observed in the pilot study (Fig 5.2). It

was located on the right P2A segment near the origin of the middle inferior temporal artery, and the

opening was long and convex-like. The second fenestration (Fig. 5.21B) had a very small slit-like

opening and was located on the left P2A segment.


105

CHAPTER SIX

DISCUSSION

6 DISCUSSION


106

6.1. ANTERIOR CEREBRAL ARTERY

6.1.1. Diameter and length

When considering the use of an artery for surgery, important factors include the diameter and the

length234. Measuring these parameters can therefore aid in the planning for certain cerebral surgeries.

The A3 segment is a dominant place for revascularisation procedures, thus adequate knowledge on the

diameter, length and possible variations at this site is essential. The number of branches originating from

this segment should also be taken into account. Cerebral revascularisation is important for treatment of

tumours, intracranial aneurysms and ischemic diseases. Adequate information on the length of possible

crossing branches between hemispheres can be crucial for safe surgeries234.

Few authors have measured the A2, A3 and A4 segments and few divided the results into the left and

right sides. Swetha76 stated that the diameter of the left and right A2 and A3 segments were the same

although the length of the left A2 segment and right A3 segments were slightly longer. This was also

observed in the present study (Table 5.4). Few studies commented on possible differences bilaterally,

between males and females, between different population groups and different age groups. These

assessments could possibly indicate patients or populations with a higher risk.

A short vessel with a large diameter provides better blood supply compared to a smaller and longer (more

tortuous course) vessel, since blood will take longer to reach the area of the brain it needs to supply. On

average (not statistically significant), the A2, A3, A4 segments had largest diameters on the left, in males,

in the specimens from the white population group, and in age Group 2. The length was shortest on the

left, in females, in the specimens from the coloured population group, and in age Group 1. Thus, the left

side showed the only prominent difference in supplying areas of the brain with shorter, larger arteries.

On average, the ACA cortical branches had largest diameters on the left, in males, in specimens from

the coloured and black population groups, and in age Group 3. The length was shortest on the left, in

females, in the specimens from the black population group, and in age Group 2. Thus, the left side and

specimens from the black population group showed the only prominent difference in supplying areas of

the brain with shorter, larger arteries. Only a few statistically significant differences were observed in

the present study and this is tabulated in Table 5.4 and Table 5.5.


107

Various studies report different average lengths of the ACA cortical branches and this may indicate

marked differences between populations groups. Therefore, more population specific studies need to be

conducted on the length of these arteries. No triplication or other anomalies were observed in the pilot

study, which emphasizes the necessity for a large sample size to ensure that rare variations are observed.

Possible differences between populations, sex, bilateral variation, age and population group, may exist.

Studies should continue to report on variation in the cerebral vasculature since undocumented variations

or anomalies can still be observed. These results should be reported to ensure neurosurgeons are aware

of these rare cases of variations and anomalies.

The different ACA segments have been defined and the division of the A4 and A5 segments are described

as a point divided close to the coronal suture in lateral view8. This cannot be seen in cadaver studies

since the brain is removed from the calvarium during the standard procedure (section 4.2, p. 44). Thus,

the marker used in cadaver studies can be similar although not identical. The diameter and length of

differently conducted studies (cadaver versus angiographic studies) will therefore not be comparable8.

Cadaver studies do not state which points were used to differentiate the A4 and A5 segments, thus in the

present study the midpoint of the corpus callosum was used as a division point between the A4 and A5

segment.

6.1.2. Presence, duplication, and triplication

The presence of the ACA cortical arteries are in accordance with previous studies2, 3, 14, 16, 17, 21, 22. Few

studies comment on the frequency of the IFA (observed in 31.6% in the pilot study and in 29.8% in the

present study) although Ugur et al.2 observed the internal frontal artery in 58.0% of cases (29 cases).

The CmA was only observed in 31.6% and 12.4% of cases in the pilot and present study, respectively,

although the CmA was observed in 40.0% to 93.4% (Table 2.1)2, 3, 14-18, 20-26 of cases in the literature.

This variability can be due to the different definitions that are used for this callosomarginal artery25.

Few studies state the duplication or triplication frequencies of the cortical ACA branches2, 3, 15.

Duplication of the IfO have been observed in 6.0% to 42.0%2, 3, 15 although the IfO was not duplicated

in either the pilot or the present study. When the brain is removed from the head, damage can occur,

specifically in the anterior frontal region. Care should be taken to not damage the arteries, specifically

the IfO and frontopolar artery. If artefactual damage occurs those specimens should be excluded from


108

the study. This could explain possible differences in the presence or absence of cortical arteries observed

by different studies.

6.1.3. Origins

Previous studies have mentioned the origins of the ACA cortical branches2, 3, 14, 16, 17, 21, 22. The origins of

the cortical branches observed in the pilot and present study are in accordance with previous studies2, 3,

14, 16, 17, 21, 22, although few studies mention the anomalous origins or common trunks. Cortical branches

can occasionally originate from the A1 segment, although this is very rare235. The IfO is usually the only

cortical branch reported to arise from the A1 segment235, although anomalous branching of the infra-

orbital artery is very rare236. Hong236 observed an IfO arising from the middle third of the A1 segment

and stated that this artery can be mistaken for the FpA or the median ACA, since this anomalous artery

was larger than usual236. Lee and Eastwood237 observed an IfO that originated from the A1 segment of

the contralateral hemisphere. In the present study the IfO and AIFA originated as a common trunk from

the A1 segment in one case.

The CmA origin varies considerably and can arise from the A2, A3 or the A4 segment and rarely from

the A1 segment8, 19. Krishnamoorthy235 observed a case of the CmA arising from the A1 segment, and

Ugur et al.20 observed the CmA and frontopolar artery originating as a common trunk from the proximal

A2 segment. In the present study the CmA originated from the AcoA in one case. This can also be viewed

as early bifurcation of the ACA into the callosomarginal and pericallosal arteries.

The CmA is defined as an artery that runs near the cingulate sulcus and gives rise to two or more cortical

branches. This artery was further classified into an atypical CmA (one or two very short arteries coursing

in the cingulate sulcus), and a typical CmA (longer course compared to an atypical callosomarginal

artery and usually originates from the A3 segment).

All the callosomarginal arteries observed (in the pilot and present study) coursed in the cingulate sulcus

and gave rise to at least two cortical branches. Therefore, all the CmAs had a typical configuration. When

a branch gives rise to only the frontal branches (IfO and the FpA excluded), it is referred to as the internal

frontal artery. Thus, even though this branch may run in the cingulate sulcus and give rise to two or three

branches, it is referred to as the IFA. This distinction is important and is not clearly explained or


109

mentioned in the literature. The most consistent branch to originate from the CmA, is the MIFA235 and

this was observed in the present study.

The CmA originating from the AcoA (one case in the present study) can be wrongly classified as a

MedACA. The CmA runs in the cingulate sulcus and not near the corpus callosum sulcus. The median

ACA usually runs in the corpus callosum sulcus or above the corpus callosum (observed in all seven

cases in the present study). The CmA only supplied one hemisphere, although the MedACA can also be

unilateral. If the course of the CmA is not followed, the artery could have been incorrectly classified as

a MedACA. This highlights the importance of examining the entire course of the artery or branch.

The IIPA typically originates from the ACA and supplies the inferior third of the precuneus. This artery

originated from the posterior cerebral artery in 40.0% of cases in the pilot study, and in 44.6% of cases

in the present study. Ladziński and Maliszewski205 observed both the inferior and superior internal

parietal arteries arising from the posterior cerebral artery in one case (1.1%), and the IIPA arising from

the posterior cerebral artery in five cases (5.3%). It is normally described that the SIPA and IIPA both

supply the precuneus. However, Beevor238 stated that the most frequent supply of the ACA did not

include the precuneus; only the maximal supplied area includes the precuneus. The area most commonly

supplied by the PCA included the precuneus, and Beevor238 observed the posterior cerebral artery

supplying the precuneus to the intraparietal sulcus on the medial surface in 40.0% of cases. Van der

Zwan et al.75 stated that in certain cases the PCA can supply part of the medial surface normally supplied

by the SIPA or IIPA and the boundary between the anterior and posterior cerebral arteries was the

parieto-occipital sulcus in only 38.0%.

The IIPA should not be mistaken for the splenial artery. The splenial artery supplies the splenium of the

corpus callosum and, according to the literature88, 199, 203, usually originates from the P2P segment or

PoA. The IIPA supplies the inferior third of the precuneus. It is thus important to mention that the IIPA

does not necessarily originate as a cortical branch from the anterior cerebral artery; it can originate from

the posterior cerebral artery. This also highlights the importance of examining the entire course of the

artery or branch.

The IIPA was not a very consistent artery since there was no visible artery in 26.3% (five cases) in the

pilot study, and in 30.6% (38 cases) in the present study. The posterior supply of the ACA depends on


110

the extent of the PCA supply and the splenial branches8. If there are variations in the anterior cerebral

artery, the PCA can supply those areas76. Rhoton8 stated that the IIPA was the least frequent branch and

is only observed in 64.0% of specimens. In contrast, Moscow et al.18 observed the IIPA in all cases,

often multiple branches.

6.1.4. Anomalies

There were no fenestrations observed in the pilot or present study, although fenestrations of the anterior

circulation have been observed by several authors in the literature32, 36, 47, 53, 55, 56, 58, 62, 68, 74, 99, 103-110, 239.

Insufficient data is available on the frequency and precise location of ACA fenestrations. A large post-

mortem study may help resolve this issue106. The azygos ACA was not observed in either the pilot or the

present study and therefore supports the notion of scarcity. Only a few authors have observed this

variation in the literature, usually as a case study2, 3, 10, 19-21, 24, 36, 47, 49, 51, 53-69, 72, 240, 241. A few studies

mislabelled the azygos ACA as the MedACA, since the azygos ACA can develop due to embryological

persistence of the median artery of the corpus callosum. Care should be taken when comparing results

from different studies to ensure that the same variation is being compared.

Median anterior cerebral arteries have been observed by numerous authors in the literature3, 17, 19, 21, 22, 25,

26, 32, 33, 36, 49, 53, 54, 57, 59, 62, 64-69, 76, 78-88, 239, 242. The MedACA was not observed in the pilot study; however,

it was observed in seven cases (11.6%) in the present study. Only four cases were bilateral; therefore the

MedACA does not always supply both hemispheres. In 381 specimens, Baptista54 observed unilateral

MedACA in 27 cases, and bilateral MedACA in 23 cases.

Bihemispheric anterior cerebral arteries have been observed by various authors in the literature14, 15, 19,

20, 22, 25, 26, 36, 54, 61, 74-76. The bihemispheric ACA was not observed in the pilot study; however, it was

observed in 12 cases (19.8%) in the present study. Branches from the left hemisphere gave branches to

the right hemisphere in seven cases, and the reverse in five cases. In 381 specimens, Baptista54 observed

branches from the left hemisphere giving branches to the right hemisphere in 25 cases, and the reverse

in 20 cases.

The definitions of a MedACA and a BihemACA can be very similar. Bihemispheric ACA is defined as

the presence of a branch that supplies the contralateral hemisphere, and the ipsilateral ACA is hypoplastic

or terminates early8, 13-15, 19, 41, 45, 46, 53. The definition of the MedACA is the presence of an additional


111

branch, and the ACA is still present and not hypoplastic3, 11, 41, 46, 54, 62, 70, 77. Additional classification is

needed for these anomalies. The definition of the BihemACA state that the ACA of the ipsilateral

hemisphere (hemisphere that receives the branch) will terminate early or be hypoplastic. It is important

to mention that in the 12 cases of bihemispheric branches, the ACA could terminated at the level of the

SIPA (two cases), PLA (five cases), PIFA (one case), MIFA (three cases) or the AIFA (one case). Thus

this definition is not necessarily accurate and extended criteria are needed. The following criteria are

suggested:

a) If the abnormal artery originates proximal to the first cortical artery, it is considered a median ACA

(artery can supply one or both hemispheres, or only one cortical artery).

b) If the abnormal artery originates distal to the first cortical artery and supplies the contralateral

hemisphere, it is considered a bihemispheric branch.

c) If the unusual artery originates distal to the first cortical artery and supplies the ipsilateral

hemisphere, it is considered a cortical artery with an abnormal origin. Figure 5.12 illustrates the

extended criteria of the median ACA, bihemispheric ACA and the unusual cortical artery.

These extended criteria can be illustrated in a comparison between Case 2 (MedACA) (Fig. 5.8) and

Case 7 (BihemACA) (Fig. 5.9). Both these cases had an unusual branch that gave origin to the SIPA. In

Case 2 (MedACA), the branch originated from the AcoA (thus proximal to the first cortical artery) and

was therefore termed a median ACA. In Case 7 (BihemACA) the abnormal branch originated from the

level of the first cortical artery, thus the abnormal branch was termed a cortical artery (SIPA) with an

unusual origin. There was a BihemACA present, and a bihemispheric and median ACA can be observed

in the same specimen, although not in this specific case. Case 1 (MedACA) was also similar to Case 11

(BihemACA). In Case 1 (MedACA) the abnormal artery originated proximal to the first cortical artery

and was therefore termed a median ACA. In Case 11 (BihemACA) the abnormal artery originated after

the first cortical artery, and was therefore termed a bihemispheric branch.


112

6.2. MIDDLE CEREBRAL ARTERY


A shorter vessel with a larger diameter is more efficient at supplying blood. Few studies comment on

possible differences that could be observed bilaterally, between males and females, between different

population groups and different age groups. On average (not statistically significant), the M1 segment

and the inferior, middle and superior trunks had similar diameters bilaterally, and largest diameters in

the specimens from the white population group, and in age Group 3. On average, the MCA cortical

branches had largest diameters on the left, in females, in the specimens from the white population group,

and in age Group 2 and 3. The length was shortest on the right, in females, in the specimens from the

black population group, and in age Group 1. Thus, the female specimens showed the only prominent

difference in supplying areas of the brain with shorter, larger arteries. Only a few statistically significant

differences were observed in the present study and this is tabulated in Table 5.8 and Table 5.10.

Literature states that the left hemisphere usually has a growth advantage and that there is left hemispheric

dominance131.

The M1 segment diameter was statistically significantly larger in specimens from the white and coloured

population groups, and in the oldest age group. There were no statistically significant differences

observed bilaterally or between males and females for the M1 diameter. Similarly, Idowu et al.113 and

van der Zwan et al.231 stated that there were no statistically significant differences observed bilaterally

in the M1 diameter and Idowu et al.113 stated that there were no statistically significant differences

between males and females. Zurada et al.233 stated that the M1 diameter remained constant with age and

Tarasów et al.232 stated that the M1 diameter was larger in people older than 40, although this was not

statistically significant.

The literature mostly states that the vessel diameters are larger in males compared to females232. Tarasów

et al.232 did observe larger diameters in males; however, this was not statistically significant. The length

of the APA was the only cortical branch to indicate a statistically significant difference between males

and females. In females the length was statistically significantly shorter, and the diameter was larger,

although not statistically significantly different.


113

Few studies comment on possible population group differences and the diameter of the CTA was the

only cortical branch to indicate a statistically significant difference between the coloured and white

population groups. The specimens from the white population group had a statistically significantly larger

diameter compared to the coloured population group; however, there were very few specimens in the

white population group (eight MCA specimens) in this study.

In the present study, comparison of age indicated the most statistically significant differences between

diameter and length of MCA cortical branches. In contradiction to the previous comparisons, these

arteries were longer in the older age group, although the arteries had either the same diameter or a smaller

diameter. In bilateral and sex comparison, when the diameter or length was statistically significantly

different, a side or a sex was usually benefitted. This is not the case with the age groups. A shorter length

does not necessarily equal a larger diameter, and vice versa. Age-related variation in diameter of vessels

can be due to compensative widening due to weakening of the elasticity in the artery wall and presence

of atherosclerosis232. In the present study, the older group indicated mostly larger diameters compared

to the younger age group.

6.2.2. Predivision length

Confusion exists on the classification of the M1 segment, in particular the distinction of the M1 segment

from the M2 segment112. The M1 segments can be defined as the part from the origin of the MCA to the

main bifurcation, or this segment can be defined as the part from the origin of the MCA to the genu

(division or no division present)124. Thus, the M1 segment length and predivision length is not always

the same, and this can lead to confusion and data to be incomparable. In Table 5.9, the length is

considerably different between certain studies. The predivision length was between 13.0 mm and 23.4

mm112, 113, 116, 123, 124, 128, 231-233. The authors should always state which definitions are being used.

In certain cases in the present study, the predivision length was very long. It should be considered that

after a certain length, the MCA branching can be classified as monofurcation. Grellier et al.116 described

monofurcation as branching after the limen insulae. However, using different definitions could cause the

frequency of monofurcation to be incorrectly described in the literature. Authors should describe the

criteria and definitions that are used to ensure the results are comparable.


114

6.2.3. Absence, duplication, triplication

The most commonly absent artery was the common temporal artery in 65.0% (13 cases) in the pilot study

and 51.0% (51 cases) in the present study. The most commonly duplicated branch was the anterior

parietal artery in 30.0% (six cases) in the pilot study and 9.0% (nine cases) in the present study. Bradac13

reported that the APA is usually a single branch. In the present study the central artery was also

commonly duplicated (8.0%). Salamon and Huang27 stated that duplication of the central artery was

almost constant. No triplication was observed in the pilot study and the only triplicated arteries in the

present study were the central and angular arteries in one case each. Very few studies report on absence,

duplication and triplication of the MCA cortical branches. Therefore, a complete description is given in

Table 5.11.

6.2.4. Origins

When bifurcation was observed in the pilot and present study, the superior trunk usually gave origin to

the OfA, PfA, precentral, and the central arteries. The parietal and angular arteries originated from either

the superior or the inferior trunks. The inferior trunk gave origin to the temporal and temporo-occipital

arteries. This is consistent with previous reports8, 11, 13, 27, 114, 121, 123, 132.

True trifurcation was only observed in the present study in six cases. When trifurcation was observed,

the superior trunk usually gave origin to the OfA, PfA and precentral arteries. The middle branch gave

origin to the central artery (three cases), APA (five cases) and PPA (three cases). The PcA and angular

arteries originated from the middle trunk in one case each. The inferior trunk usually gave origin to the

temporal, temporo-occipital and angular arteries. These findings are consistent with previous reports8, 11,

13, 27, 114, 121, 123, 132.

Few studies mention distinct origins, and although authors commonly state that cortical branches can

arise from common trunks, few studies discuss the prevalence of these common trunks132. The common

trunks were described in detail in the results section 5.2 (p. 54) and 5.5.2.3. (p. 83). It is noteworthy to

mention the definition of a common trunk. A common trunk was defined when the arteries bifurcated,

and one artery did not arise from the other artery. A common trunk typically bifurcates at almost a 90

degree angle and the cortical branches have similar diameters. This is not always defined in the literature

and could lead to inaccurate results. Furthermore a cortical branch could originate from another cortical

branch, and this has not been discussed in previous studies.


115

6.2.5. Early branches

Cortical branches that arise from the main MCA trunk before the initial branching are referred to as early

branches. Early branches were observed in the present study in 85.0% of cases. Most authors only state

that early frontal or temporal branches were present, although the specific cortical branches that arose as

early branches are rarely mentioned. Meneses et al.123 stated that the TpA originated as an early temporal

branch in 80.0%, the ATA in 40.0%, the orbitofrontal artery in 30.0%, and the middle and posterior

temporal arteries in 20.0%. Idowu et al.113 stated that the only early temporal branch was the TpA and

the only early frontal branch was the OfA. In the present study the OfA, PfA, temporopolar artery and

anterior temporal artery frequently arose as early branches.

6.2.6. Branching

Eleven branching subtypes can be distinguished from the literature. Most authors do not specify the

different branching subtypes. The only branching types usually mentioned include bifurcation,

trifurcation, monofurcation and tetrafurcation. The definitions used to classify the branching types need

to be equivalent; otherwise the results will not be comparable. In Figure 2.6 (section 2.2.2, p. 22) these

11 branching subtypes are described in detail, to ensure that future studies will not report incorrect

results. When definitions are adequately described, future studies can be compared to ascertain possible

differences in sex, population group and different age groups.

Tanriover et al.114 stated that in the trifurcation cases observed, the middle trunk gave rise to either one

or two arteries. This was also observed in the present study (two arteries in four cases, three arteries in

two cases). The middle trunk never gave rise to just one artery, although it is noteworthy that the superior

trunk in certain trifurcation cases only gave rise to one artery (the calcarine artery in two cases). This

could be perceived as the cortical branch arising with a large diameter at the bifurcation region. Currently

only the branching region is being taken into account when the branching type is classified and not the

arteries that the trunks give rise to.

Ugur et al.20 stated that the middle trunk was observed in 75.0% of cases, although the authors further

elaborated that this middle trunk originated from the superior trunk in 62.5% and from the inferior trunk

in 12.5%. This shows that true trifurcation was not observed, and it is more likely that the authors

observed pseudotrifurcation, medial or lateral trifurcation. Not all authors give further description of the

trifurcation cases. Most studies do not state the distances used to define these branching types. Only the


116

terms “close,” “near” and “the impression of branching” are used as terminology. Ciszek et al.133 stated

that a second early temporal branch with a large diameter can create a “false bifurcation” and Vuillier et

al.124 stated that the cortical branches can be mistakenly classified as branching. Pseudobifurcation is

described as only medial pseudobifurcation and pseudobifurcation. The term “lateral” was added to

avoid confusion. Since the previous authors did not state the criteria, this was determined in the pilot

study (section 5.2, p. 52).

Early branching was classified when the first major division occurred at 5 mm or less from the MCA

origin117-120. Only one case (1.0%) in the present study fits these criteria and therefore it should be

considered to modify this definition to branching before 8 mm or even 10 mm. If these modified criteria

are used (branching before 8 mm), then the frequency of early branching would have been 7.0%. This is

still in the reported frequency as described in the literature by previous authors. Early branching has been

observed in 2.6% to 11.3%32, 82, 118, 119, 131 of cases. Authors need to state what is considered as early

branching, and possibly give the length of each case observed. Therefore future studies can adjust the

observations to compare the literature with their results.

Few studies fully describe the MCA branching subtypes and very few studies comment on possible

differences between males and females, the left and right side, different population groups and different

age groups. In the present study, there was a statistically significant differences between the branching

subtypes in comparison between males (n=68) and females (n=32). Idowu et al.113 observed no

difference in the branching pattern between males and females.

6.2.7. Anomalies

Several authors have observed an accessory MCA6, 7, 32, 33, 36, 55, 56, 82, 99, 105, 106, 113, 114, 116, 121-123, 130, 145, 147,

148, 150, 154, 158, 159, 183, 243-247, a duplicated MCA6, 32, 33, 116, 118, 119, 122, 123, 130, 131, 134, 142-151, 171, 172, 244, 248, and

fenestration of the MCA58, 93, 107, 120, 122, 124, 125, 145, 148, 150, 161, 168, 239, 249. In the pilot and present study an

accessory, duplicated or a fenestrated MCA were not observed. This demonstrates the necessity for larger

studies on the MCA, since these variations are extremely rare. There is a gap in the literature regarding

data on the MCA anatomy and variations, and more data should be obtained on the diameter, length, and

the area supplied by these anomalies.


117

Very few details are given on the diameter and area supplied by the duplicated MCA. The diameters of

the duplicated MCA have been documented as 1.4 mm and 3.5 mm by Meneses et al.123 and Umansky

et al.122, respectively. Meneses et al.123 stated that the duplicated MCA supplied the temporopolar artery

and the ATA. Few details are given on the diameter of the accessory MCA and this has been documented

as 1.1 mm to 1.6 mm122, 123, 158. Kim and Lee154 stated that in 18.8% the diameter of the accessory middle

cerebral artery was similar to the main MCA trunk, and in 81.3% it was smaller compared to the main

MCA trunk.

The accessory MCA arises from the anterior cerebral artery, however, few authors state the precise

origin. It has been observed arising from the A1 segment116, near the AcoA area158, 245, the proximal A1

segment154, the middle A1 segment154, the distal A1 segment154, and the A2 segment154. Studies may

confuse the proximal and distal A1 segments. The proximal part is closest to the origin of the A1 segment

(at the connection of MCA) and the distal A1 segment is closest to the origin of the AcoA.

Few authors state which cortical branches are supplied by the additional branch or what area is supplied

by the additional vessel. The AccMCA usually supplies the frontal region and the DupMCA the temporal

region. The accessory MCA generally gives rise to the orbitofrontal artery and PfA246, and the duplicated

MCA to the TpA, anterior and middle temporal arteries143. Other cortical branches that have been

supplied by the accessory MCA include the RaH123, precentral artery154, 246, 250, central artery154, 246, 250,

APA154. It is extremely important to state the precise origin, course and diameter of the accessory and

duplicated MCA since this information is helpful to neurosurgeons139. The duplicated MCA is more

scarce compared to the accessory MCA and few authors mention the areas supplied by the duplicated

MCA.

Fenestration of the MCA is usually described to have three main subtypes, proximal, intermediate and

distal fenestration, however, studies do not always state if this refers to fenestration at the M1 segment,

since fenestration can also be observed at the M2 segment. Fenestration of the MCA was observed in

0.1% to 5.8% (Table 2.7)53, 58, 93, 107, 120, 122, 124, 145, 148, 150, 161, 168 in the literature.

If the branching or origin is slightly different from the normal definition, this should be thoroughly

explained. This ensures that future studies using different or elaborated definitions can still be compared

to previous work. For example, the accessory MCA was first described as an artery arising from the ICA


118

or anterior cerebral artery. This definition was later altered; the term accessory MCA only refers to an

artery arising from the anterior cerebral artery, and the term duplicated MCA was used for an artery

originating from the ICA117. In later studies the DupMCA was further elaborated into two subtypes, Type

A arises at the top of the ICA (more distal origin), and Type B arises between the top of the ICA and

anterior choroidal artery (more proximal origin)141-143. Therefore, if previous authors and earlier studies

described the anomalies thoroughly, the data can be compared to later studies. The different MCA

anomalies are explained in section 2.25 (pp. 25-30) and a detailed line diagram is provided (Fig. 2.8) to

ensure that future studies give adequate information on the anomalies that are observed. To compare the

results of studies, the definitions that are used for the anomalies should always be reviewed.


119

6.3. POSTERIOR CEREBRAL ARTERY


A shorter vessel with a larger diameter is more efficient at supplying blood. Few studies comment on

possible differences that could be observed bilaterally, between males and females, between different

population groups and different age groups. On average (not statistically significant), the P1, P2 and P3

segments had larger diameters on the left, in males, in the specimens from the white population group,

and in age Group 3. The length was shortest on the left, in females, in the specimens from the coloured

population group, and in age Group 1. Thus, the left side showed the only prominent difference in

supplying areas of the brain with shorter, larger arteries. On average, the PCA cortical branches had

larger diameters on the left, in males, in the specimens from the white population group, and in age

Group 2. The length was shortest on the left, in females, in the specimens from the coloured population

group, and in age Group 1. Thus, the left side showed the only prominent difference in supplying areas

of the brain with shorter, larger arteries and the literature does state that the left side is usually

benefited131. Only a few statistically significant differences were observed in the present study and these

are tabulated in Table 5.14 and Table 5.15.

Zeal and Rhoton199 stated that the P2A and P2P segments were each approximately 25.0 mm in length.

In the present study the P2A and P2P segments were 39.0 mm and 13.4 mm, respectively. This difference

could be due to variances in definition of the P2A and P2P segments. Few studies mention the PCA

segment lengths; therefore this comparison may be biased. Authors should always state how the

segments were defined and measured.

The diameters were similar in the literature, and this was most likely since the same part is usually used

to measure the diameter (at the origin of the segment or branch). Not all authors state the part that was

measured and this could lead to incomparable results. Very few studies give separate data of the right

and left sides, and none give information on sex, age, or population group. This makes it impossible to

compare the results with previous studies.

6.3.2. Absence, duplication, triplication

The CTA was observed in only six cases (30.0%) in the pilot study and 34 cases (27.4%) in the present

study, which is consistent with the literature. The presence of the CTA was 16.0%199, and 20.0%204 in


120

the literature, thus the CTA is not consistent. The AITA was observed in 15 cases (75.0%) in the pilot

study and in 119 cases (96.0%) in the present study. The PITA was observed in 19 cases (95.0%) in the

pilot study and in 123 cases (99.2%) in the present study. This is consistent with the literature. The

presence of the MITA was reported in the literature as 20.0%204 and 38.0%199. The MITA was observed

in 19 cases (95.0%) in the pilot study and in 114 cases (91.9%) in the present study. This artery is

described as not very consistent, although this cortical branch was observed in most hemispheres. The

PoA and calcarine artery was observed in all cases in the pilot and present study, which is consistent

with the literature199, 201, 202. The presence of the splenial artery was reported in the literature as 90.0%201

and 100%88, 199. However, the splenial artery was observed in only four cases (20.0%) in the pilot study

and in 45 cases (36.3%) in the present study.

6.3.3. Origins

The CTA originated from the P2A segment in all cases observed in the pilot and present study. The most

common origin is reported in the literature as either the P2A or P2P segment199, 204. A common temporal

artery was defined when the arteries bifurcated, and one artery did not arise from the other artery. A

common trunk typically bifurcates at almost a 90 degree angle and the cortical branches have similar

diameters. This is not always defined in the literature and could lead to confusion and inaccurate results.

The most common origin of the AITA and MITA was the P2A segment in the literature199, 204. The most

common origin of the PITA in the literature was the P2 segment196, 202 and P2P segment199, 204. The most

common origin of the temporal arteries was the P2A segment in the pilot and present study. The most

common origin of the calcarine artery and PoA was the P3 segment in the pilot and present study,

although the PoA and calcarine artery can originate from the P2P, P3 or P4 segment. Thus the results

from the pilot and present study are similar to the descriptions in the literature.

The most common origin of the splenial artery was the PoA in the pilot and present study. In the

literature, the splenial artery also originated mostly from the PoA88, 199, 201. The prevalence observed in

comparison to previous studies varies tremendously. The IIPA originated from the posterior cerebral

artery in 40.0% of cases observed in the pilot study, and in 44.6% of cases in the present study. It is

possible that the studies mistermed the IIPA as the splenial artery. The IIPA supplies the inferior third

of the precuneus and the splenial artery supplies the splenium of the corpus callosum. This is further

described in section 6.1.3. (p. 109). The area supplied by the artery should be taken into account, not just

the origin.


121

6.3.4. Branching

The end of the main trunk was previously described as the branching of the common temporal artery;

however, the main branching is now described at the origin of the calcarine and parieto-occiptal arteries.

This point is also used when refering to the main branching point; however, this configuration was only

observed in one case (5.0%) in the pilot study and 34 cases (27.4%) in the present study. The first

branching (main bifurcation) was due to origin of the CTA in six cases (30.0%) in the pilot study and 25

cases (20.2%) in the present study. Furthermore, the main bifurcation was due to origin of the PITA in

eight cases (40.0%) in the pilot study and 52 cases (41.9%) in the present study. Trifurcation can also be

observed. A branching before the division of the PoA and calcarine artery was present in most cases.

This shows that the main branching point of the PCA should be reconsidered and should be mentioned

in subsequent studies.

Since the main branching of the PCA is described as the division between the PoA and the calcarine

artery (end of the main trunk), this level is usually noted in previous studies. This division level was

reported in in the present study (section 5.2.3, p. 100). The PoA and calcarine artery typically originate

at the P3 segment, although the branching can occur at the P2 or P4 segments205. Studies usually only

comment on the branching point of the PoA and calcarine artery and not whether a branching was

observed before this division.

It should be noted how branching is classified, since it is not just a large vessel originated from the main

stem. A visible splitting of the main trunk is seen into either two or three branches (as can be seen in the

branching of the middle cerebral artery). The branching is usually at a 90 degree angle and the vessels

have a similar diameter.

6.3.5. Anomalies

There was one case of fenestration in the pilot study and two cases of fenestration in the present study.

Fenestrations of the PCA are typically observed in the P1 segment, although not as often in the P2

segment. All three fenestrations were located in the P2A segment (two left side, one right side).

Fenestrations of the PCA are not very common and fenestrations are usually observed in the AcoA or

basilar arteries. Fenestration of the PCA was observed by various authors53, 99, 105, 107, 118, 161, 197, 211-218 in

previous studies. Few authors give more information other than the presence of the fenestration.


122

The fenestration observed in the pilot study (Fig. 5.2) and the first case described in the present study

(Fig. 5.21A) was similar and can be seen as two arteries originating nearby and then merging. The

definition of fenestration is incomplete duplication, which implies one common origin of an artery which

split into two and re-joins46, 58, 92-94. This is not the case with these two cases (fenestration 1 and

fenestration 1A). Two arteries seem to merge, not split. The second fenestration case (slit-like) represents

a typical example of incomplete duplication. The artery split into two parts, and re-joined. Fenestration

was the only true anomaly of the PCA that was observed in either the pilot or present study.


123

6.4. LIMITATIONS

Rare anomalies were not always observed in the pilot or present study, therefore, a limitation of this

study was the sample size. A larger sample size could ensure that rare variations and anomalies are

observed. A total of 136 hemispheres were used, which is more compared to most of the previous studies.

In all autopsy studies there is a risk of artefactual damage to the specimens. Damage can occur to the

brain and arterial system during the removal of the brain. If there is damage, those specimens should be

excluded to avoid misrepresentation of cortical branches. Decomposition is also possible, and if

decomposition is extreme those specimens should be excluded.

Autopsy studies measured the external diameter of the arteries, and in MRA studies the internal diameter

is measured. Thus there can be a difference in reported diameter and the results of these different types

of studies cannot be compared.

Studies conducted with the use of MRA also have limitations including certain smaller vessels not being

detected232. Cadaver studies may be useful in observing these smaller vessels, although the presence of

blood or blood clots may obstruct flow of the dyes causing the arterial systems to not fill properly251.

Possible anastomoses between cerebral arteries and cortical branches were studied, although the

coloured silicone did not always reach to the end of the artery. If the supply of a specific branch or

cerebral artery is investigated, it is important that the medium is injected into the arteries at same time,

with the same pressure for adequate visualisation of the supply of each artery238.

Subtle differences can also be evident between autopsy studies using different materials or dyes and the

consistency of the material or dyes can influence the results. Thinner fluids may fill smaller vessels more

effectively, although thicker mediums that solidify allows for better investigation of the arterial system.

A range of media have been used (described in section 4.3. p. 45)251.


124

CHAPTER SEVEN

CONCLUSION

7 CONCLUSION


125

Knowledge of the anatomy of the cerebral arteries is essential in vascular procedures, for example

aneurysm and arteriovenous malformation surgery5. In addition, information on the anatomical pattern

of the cerebral arteries is essential in interpretation of clinical signs of a stroke17, 121. Furthermore,

aneurysms can be observed at the branching of cerebral vessels, highlighting the importance of a

thorough knowledge of the vascular anatomy5, 7, 14, 119, 252. Moreover, obliteration of an arterial segment

can cause unwanted or unexpected clinical consequences due to variations in the pattern of cerebral

arteries17, 42. Variation of the length is important in neurosurgical procedures, since a shorter trunk may

play a role in aneurysm formation. Changes in vessel diameter could also indicate early signs of several

pathological conditions49.

In a comparison between the ACA, MCA and the PCA, the anterior cerebral artery has been thoroughly

studied. However, there are still aspects that have not been adequately investigated. The average

diameters, lengths and origins of the ACA cortical branches are described by selected studies, although

the common trunks are not described in the literature. This was done in the pilot and present study.

The ACA variations are described in the literature, although additional criteria were still lacking. This

was described in the results section of the present study. Most studies only mention the presence of ACA

anomalies and few authors give further information on these anomalous arteries. A thorough

investigation was conducted on the prevalence of these anomalies, and in the present study, more

information was given on the origin, diameter, length and area supplied by these anomalous branches.

The average diameters, length and origins of the MCA cortical branches are not adequately described in

the literature. Possible common trunks are also not thoroughly reported in the literature. These aspects

were reported on in the pilot and present study. The anatomy of the temporal superior arteries have been

scarcely documented, thus a detailed description was given on the anatomy of the temporal superior

arteries.

The MCA branching types are discussed in previous studies, although the different subtypes are usually

neglected; only bifurcation and trifurcation are usually noted. An illustration of the different subtypes is

given in the literature review since there is still confusion on these subtypes. The criteria for each subtype

has also not been previously described, thus this was noted in the pilot study.


126

The MCA anomalies are described in the literature and an illustration of these anomalies are given in the

literature review. Most studies only mention the prevalence of the anomalies, and this was tabulated in

the literature review. Not enough information is given when these MCA anomalies are observed, thus

an illustration was given to ensure future studies can adequately describe these anomalies.

In comparison to the anterior and middle cerebral arteries, the PCA is the most neglected cerebral artery.

The average diameters and lengths of the PCA cortical branches have not been described, and origins

have only been mentioned in selected studies. Therefore, this was done in the pilot and in the present

study. This study proposes a revised classification of the inferior temporal arteries, which excludes the

hippocampal arteries, and takes into account the origins of the inferior temporal cortical branches of the

PCA. Therefore, the configuration of the temporal arteries was also discussed in detail. The branching

pattern has been described as the main branching between PoA and calcarine artery. This was not the

case in the majority of cases. Therefore the branching pattern was re-evaluated and described as

monofurcation, bifurcation and trifurcation.

The PCA anomalies have been described in the literature and an indication on the prevalence is given in

the literature review. Fenestration of the PCA is very rare, although one case was observed in the pilot

study and two cases in the present study. Digital images of these fenestration were provided to contribute

to the knowledge on these anomalies.

Possible differences between age, population groups, sex and bilateral variation regarding the diameter

and length of the cerebral segments and cortical branches are, to the author’s best knowledge, not

mentioned or poorly reported in previous studies. Therefore in the present study a detailed analysis was

done to indicate possible statistically significant differences. The ACA and PCA segments and cortical

branches usually indicated larger diameters and shorter lengths on the left side and the MCA cortical

branches showed larger diameters and shorter lengths in females. The pilot and present study also

reported on the origins, absence, duplication and triplication of the cortical branches, since limited

research with regard to these aspects have been conducted.

The brains were obtained from Stellenbosch University and from a Western Cape population. To the

author’s best knowledge, no studies of this nature have previously been completed on a Western Cape

population or in South Africa. Given the important implications that the anatomical variation of the


127

cerebral arteries may have, future research should focus on giving a more comprehensive description of

the anatomy.


128

REFERENCES

1. Chusid JG. Correlative Neuroanatomy & Functional Neurology. 18th ed. California: Lange

Medical publications; 1982.

2. Ugur HC, Kahilogullari G, Esmer AF, Combert A, Kanpolat Y. A neurosurgical view of anatomical

variations of the distal anterior cerebral artery: an anatomical study. Journal of Neurosurgery.

2006;104:1-7.

3. Stefani MA, Schneider FL, Marrone ACH, Severino AG, Jackowski AP, Wallace MC. Anatomic

Variations of Anterior Cerebral Artery Cortical Branches. Clinical Anatomy. 2000;13:231-236.

4. Izci Y, Seçkin H, Medow J, Turnquist C, Başkaya MK. Sulcal and gyral anatomy of the

orbitofrontal cortex in relation to the recurrent artery of Heubner: an anatomical study. Surgical

and Radiologic Anatomy. 2009b;31(6):439-445.

5. Kahilogullari G, Ugur HC, Comert A, Tekdemir I, Kanpolat Y. The branching pattern of the middle

cerebral artery: is the intermediate trunk real or not? An anatomical study correlating with simple

angiography Laboratory investigation. Journal of Neurosurgery. 2012;116(5):1024-1034.

6. Tanriover N, Kawashima M, Rhoton AL, Ulm AJ, Mericle RA. Microsurgical anatomy of the early

branches of the middle cerebral artery: morphometric analysis and classification with angiographic

correlation. Journal of Neurosurgery. 2003;98:1277-1290.

7. Gibo H, Carver CC, Rhoton AL, Lenkey C, Mitchell RJ. Microsurgical anatomy of the middle

cerebral artery. Journal of Neurosurgery. 1981;54:151-169.

8. Rhoton AL. The supratentorial arteries. Neurosurgery. 2002;51(4):53-120.

9. Pai BS, Varma RG, Kulkarni RN, Nirmala S, Manjunath LC, Rakshith S. Microsurgical anatomy

of the posterior circulation. Neurology India. 2007;55(1)31-41.

10. Gunnal SA, Wabale RN, Farooqui MS. Variations of anterior cerebral artery in human cadavers.

Neurology Asia. 2013;18(3):249-259.

11. Krayenbuhl H, Yasargil MG, Huber P. Cerebral Angiography. Thieme Medical Publishers; 1982.

12. Osborn AG, Jacobs JM. Diagnostic Cerebral Angiography. 2th ed. Lippincott Williams & Wilkins;

1999.

13. Bradac GB. Cerebral Angiography- Normal Anatomy and Vascular Pathology. London: Springer;

2011.

14. Perlmutter D, Rhoton AL. Microsurgical anatomy of the distal anterior cerebral artery. Journal of

Neurosurgery. 1978;49:204-228.


129

15. Ring BA, Waddington MM. Roentgenographic anatomy of the pericallosal arteries. The American

Journal of Roentgenology, Radium Therapy, and Nuclear Medicine. 1968;104:109-118.

16. Cavalcanti DD, Albuquerque FC, Silva BF, Spetzler RF, Preul MC. The anatomy of the

callosomarginal artery: applications to microsurgery and endovascular surgery. Neurosurgery.

2010;66(3):602-610.

17. Kakou M, Destrieux C, Velut S. Microanatomy of the pericallosal arterial complex. Journal of


18. Moscow N, Michotey P, Salamon G. Anatomy of the cortical branches of the anterior cerebral

artery. Radiology of the skull and brain. 1974 (2):1411-1420.

19. Lehecka M, Dashti R, Hernesniemi J, Niemelä M, Koivisto T, Ronkainen A, Rinne J, Jääskeläinen

J. Microneurosurgical management of aneurysms at the A2 segment of anterior cerebral artery

(proximal pericallosal artery) and its frontobasal branches. Surgical Neurology. 2008;70(3):232-

246.

20. Ugur HC, Kahilogullari G, Coscarella E, Unlu A, Tekdemir I, Morcos JJ, Elhan A, Baskaya MK.

Arterial vascularization of primary motor cortex (precentral gyrus). Surgical Neurology.

2005;64(2):48-52.

21. Gomes FB, Dujovny M, Umansky F, Berman SK, Diaz FG, Ausman JI, Mirchandani HG, Ray WJ.

Microanatomy of the anterior cerebral artery. Surgical Neurology. 1986;26(2):129-141.

22. Kedia S, Daisy S, Mukherjee KK, Salunke P, Srinivasa R, Narain MS. Microsurgical anatomy of

the anterior cerebral artery in Indian cadavers. Neurology India. 2013;61(2):117-121.

23. Lemos VPJ. Frequency of the callosomarginal artery and proposal of a hypothesis with regard to

its phylogenetic significance. Arquivos de Neuro-Psiquiatria. 1984;42(4):335-340.

24. Nowinski WL, Thirunavuukarasuu A, Volkau I, Marchenko Y, Aminah B, Puspitasari F, Runge

VM. A three-dimensional interactive atlas of cerebral arterial variants. Neuroinformatics.

2009;7(4):255-264.

25. Saidi H, Kitunguu PK, Ogeng'O JA. Variant anatomy of the anterior cerebral artery in adult brains.

African Journal of Neurological Sciences. 2008;27(1):97-105.

26. Stefani MA, Schneider FL, Marrone ACH, Severino AG. Influensce of the gender on cerebral

vascular diameters observed during the magnetic resonance angiographic examination of Willis

circle. Brazilian Archives of Biology and Technology. 2013;56(1):45-52.

27. Salamon G, Huang YP. Radiologic anatomy of the brain. Springer Science & Business Media;

1976.


130

28. Ramos A, Chaddad-Neto F, Joaquim AF, Campos-Filho JM, Mattos JP, Ribas GC, Oliveira ED.

The microsurgical anatomy of the gyrus rectus area and its neurosurgical implications. Arquivos

de Neuro-Psiquiatria. 2009;67(1):90-95.

29. Avci E, Fossett D, Aslan M, Attar A, Egemen N. Branches of the anterior cerebral artery near the

anterior communicating artery complex: an anatomic study and surgical perspective. Neurologia

Medico-chirurgica. 2003;43(7):329-333.

30. Kawashima M, Matsushima T, Sasaki T. Surgical strategy for distal anterior cerebral artery

aneurysms: microsurgical anatomy. Journal of Neurosurgery. 2003;99(3):517-525.

31. Jinkins JRL. Atlas of Neuroradiologic Embryology, Anatomy, and Variants. Lippincott Williams

and Wilkins: 2000.

32. Ozaki T, Handa H, Tomimoto K, Hazama F. Anatomical variations of the arterial system of the

base of the brain. Archiv für Japanische Chirurgie. 1977;46:3-17.

33. Jain KK. Some Observations on the Anatomy of the Middle Cerebral Artery. Canadian Journal of

Surgery. 1964;7:134-139.

34. Ladziński P, Maliszewski M, Majchrzak H. The accessory anterior cerebral artery: case report and

anatomic analysis of vascular anomaly. Surgical Neurology. 1997;48(2):171-174.

35. Burbank NS, Morris PP. Unique anomalous origin of the left anterior cerebral artery. American

Journal of Neuroradiology. 2005;26(10):2533-2535.

36. Kovač JD, Stanković A, Stanković D, Kovač B, Šaranović D. Intracranial arterial variations: A

comprehensive evaluation using CT angiography. Medical Science Monitor: International Medical

Journal of Experimental and Clinical Research. 2014;20:420.

37. Hashizume K, Nukui H, Horikoshi T, Kaneko M, Fukamachi A. Giant aneurysm of the azygos

anterior cerebral artery associated with acute subdural hematoma-case report. Neurologia Medico-

chirurgica. 1992;32(9):693-697.

38. Baykal S, Ceylan S, Dinç H, Soylev E, Usul H, Akturk F. Aneurysm of an azygos anterior cerebral

artery: report of two cases and review of the literature. Neurosurgical Review. 1996;19(1):57-59.

39. Cinnamon J, Zito J, Chalif DJ, Gorey MT, Black KS, Scuderi DM, Hyman RA. Aneurysm of the

azygos pericallosal artery: diagnosis by MR imaging and MR angiography. American Journal of

Neuroradiology. 1992;13(1):280-282.

40. Critchley M. Syndromes of the Anterior Cerebral Artery. Royal Society of Medicine.

1930;23(5):630-632.


131

41. Dimmick SJ, Faulder KC. Normal variants of the cerebral circulation at multidetector CT

angiography. Radiographics. 2009;29(4):1027-1043.

42. Hussain Z, Corkill RA, Kuker W, Byrne JV. Distal aneurysms of the unpaired ACA: embryologic

and therapeutic aspects. Neuroradiology. 2005;47(3):209-214.

43. Katz RW, Horoupian DS, Zingesser L. Aneurysm of azygous anterior cerebral artery. A case

report. Journal of Neurosurgery. 1978;48(5):804-808.

44. Milenković Z, Vucetić R, Puzić M. Asymmetry and anomalies of the circle of Willis in fetal brain.

Microsurgical study and functional remarks. Surgical Neurology. 1985;24(5):563-570.

45. Okahara M, Kiyosue H, Mori H, Tanoue S, Sainou M, Nagatomi H. Anatomic variations of the

cerebral arteries and their embryology: a pictorial review. European Journal of Radiology.

2002;12(10):2548-2561.

46. Parmar H, Sitoh YY, Hui F. Normal variants of the intracranial circulation demonstrated by MR

angiography at 3T. European Journal of Radiology. 2005;56(2):220-228.

47. Ihara S, Uemura K, Tsukada A, Yanaka K, Nose T. Aneurysm and fenestration of the azygos

anterior cerebral artery-case report. Neurologia Medico-chirurgica. 2003;43(5):246-249.

48. Jennings S, Haider A. Case report: the clinical significance of an azygos anterior cerebral artery.

International Journal of Anatomical Variations. 2011;4:185-187.

49. Zurada A, Gielecki J, Tubbs RS, Loukas M, Cohen-Gadol AA, Chlebiej M, Maksymowicz W,

Nowak D, Zawiliński J, Michalak M. Three-dimensional morphometry of the A2 segment of the

anterior cerebral artery with neurosurgical relevance. Clinical Anatomy. 2010;23(7):759-769.

50. Kondo A, Koyama T, Ishikawa J, Iwaki K, Yamasaki T. Ruptured aneurysm of an azygos anterior

cerebral artery. Neuroradiology. 1979;17(4):227-229.

51. Wan-Yin S, Ming-Hua L, Bin-Xian G, Yong-Dong L, Hua-Qiao T. Azygous anterior cerebral

artery and associated aneurysms: detection and identification using 3-dimensional time-of-flight

magnetic resonance angiography. Journal of Neuroimaging. 2014;24(1):18-22.

52. Kathuria S, Gregg L, Chen J, Gandhi D. Normal cerebral arterial development and variations.

Seminars in Ultrasound, CT and MRI. 2011;32(3):242-251.

53. Hamidi C, Bükte Y, Hattapoğlu S, Ekici F, Tekbaş G, Önder H, Gümüş H, Bilici A. Display with

64-detector MDCT angiography of cerebral vascular variations. Surgical and Radiologic Anatomy.

2013;35(8):729-736.

54. Baptista AG. Studies on the Arteries of the Brain. ii. The Anterior Cerebral Artery: Some Anatomic

Features and their Clinical Implications. Neurology. 1963;13:825-835.


132

55. Sanders WP, Sorek PA, Mehta BA. Fenestration of intracranial arteries with special attention to

associated aneurysms and other anomalies. American Journal of Neuroradiology. 1993;14(3):675-

680.

56. Wollschlaeger G, Wollschlaeger PB, Lucas FV, Lopez VF. Experience and result with postmortem

cerebral angiography performed as routine procedure of the autopsy. The American Journal of

Roentgenology, Radium Therapy, and Nuclear Medicine. 1967;101(1):68-87.

57. Avci E, Fossett D, Erdogan A, Egemen N, Attar A, Aslan M. Perforating branches of the

anomalous anterior communicating complex. Clinical Neurology and Neurosurgery.

2001;103(1):19-22.

58. Bharatha A, Aviv RI, White J, Fox AJ, Symons SP. Intracranial arterial fenestrations: frequency

on CT angiography and association with other vascular lesions. Surgical and Radiologic Anatomy.

2008;30(5):397-401.

59. Dunker RO, Harris AB. Surgical anatomy of the proximal anterior cerebral artery. Journal of

Neurosurgery. 1976;44(3):359-367.

60. Fisher CM. The Circle of Willis: Anatomical Variations. Annals of Vascular Diseases. 1965;2:99-

105.

61. Huber P, Braun J, Hirschmann D, Agyeman JF. Incidence of berry aneurysms of the unpaired

pericallosal artery: angiographic study. Neuroradiology. 1980;19(3):143-147.

62. Kapoor K, Singh B, Dewan LI. Variations in the configuration of the circle of Willis. Anatomical

Science International. 2008;83(2):96-106.

63. Lemay M, Gooding CA. The clinical significance of the azygos anterior cerebral artery (ACA).

The American Journal of Roentgenology, Radium Therapy, and Nuclear Medicine. 1966;98:602-

610.

64. Macchi C, Catini C, Federico C, Gulisano M, Pacini P, Cecchi F, Corcos L, Brizzi E. Magnetic

resonance angiographic evaluation of circulus arteriosus cerebri (circle of Willis): a morphologic

study in 100 human healthy subjects. Italian Journal of Anatomy and Embryology.

1996;101(2):115-23.

65. Nathal E, Yasui N, Sampei T, Suzuki A. Intraoperative anatomical studies in patients with

aneurysms of the anterior communicating artery complex. Journal of Neurosurgery.

1992;76(4):629-634.

66. Serizawa T, Saeki N, Yamaura A. Microsurgical anatomy and clinical significance of the anterior

communicating artery and its perforating branches. Neurosurgery. 1997;40(6):1211-1216.


133

67. Tulleken CA. A study of the anatomy of the anterior communicating artery with the aid of the

operating microscope. Clinical Neurology and Neurosurgery. 1978;80(3):169-173.

68. Uchino A, Nomiyama K, Takase Y, Kudo S. Anterior cerebral artery variations detected by MR

angiography. Neuroradiology. 2006b;48(9):647-652.

69. Windle BC. The Arteries Forming the Circle of Willis. Journal of Anatomy and Physiology.

1888;22(2):289-293.

70. Niederberger E, Gauvrit JY, Morandi X, Carsin-Nicol B, Gauthier T, Ferré JC. Anatomic variants

of the anterior part of the cerebral arterial circle at multidetector computed tomography

angiography. Journal of Neuroradiology. 2010;37(3):139-147.

71. Szdzuy D, Lehmann R, Nickel B. Common trunk of the anterior cerebral arteries. Neuroradiology.

1972;4(1):51-56.

72. Vasović LP. Fetal azygos pericallosal artery. Clinical Anatomy. 2006;19(4):327-331.

73. Topsakal C, Ozveren MF, Erol FS, Cihangiroglu M, Cetin H. Giant aneurysm of the azygos

pericallosal artery: case report and review of the literature. Surgical Neurology. 2003;60(6):524-

533.

74. Paul S, Mishra S. Variations of the anterior cerebral artery in human cadavers: a dissection study.

Journal of the Anatomical Society of India. 2004;53(1):15-16.

75. van der Zwan A, Hillen B, Tulleken CA, Dujovny M, Dragovic L. Variability of the territories of

the major cerebral arteries. Journal of Neurosurgery. 1992;77(6):927-940.

76. Swetha B. Anatomic features of distal anterior cerebral artery supply on corpus callosum: a detailed

study on 140 cerebral hemispheres. Journal of Neurological Sciences (Turkish). 2012;29(1):46-56.

77. Pekcevik Y, Hasbay E, Oncel D. Colloid cyst of the third ventricle associated with anterior cerebral

artery trifurcation and agenesis of the corpus callosum: findings on MRI and CT angiography.

Pediatric Radiology. 2012;42(9):1130-1133.

78. Kahilogullari G, Comert A, Arslan M, Esmer AF, Tuccar E, Elhan A, Tubbs RS, Ugur HC. Callosal

branches of the anterior cerebral artery: an anatomical report. Clinical Anatomy. 2008;21(5):383-

388.

79. Fawcett E, Blachford JV. The circle of Willis: an examination of 700 specimens. Journal of

Anatomy and Physiology. 1905;40:63-70.

80. Kulenović A, Dilberović F, Ovcina F. Variation in the flow and branching of the anterior and

middle cerebral arteries. Medical Archives. 2003;57(1):3-5. (Abstract only)


134

81. Cilliers K, Vorster W, Page BJ. The anatomical variation of the circle of Willis in a cadaver cohort

representing the population dynamics of the Western Cape (Unpublished research report).

Stellenbosch: Stellenbosch University; 2013.

82. Kayembe KN, Sasahara M, Hazama F. Cerebral aneurysms and variations in the circle of Willis.

Stroke. 1984;15(5):846-850.

83. Kwak R, Niizuma H, Hatanaka M, Suzuki J. Anterior communicating artery aneurysms with

associated anomalies. Journal of Neurosurgery. 1980;52(2):162-164.

84. Marinković S, Milisavljević M, Marinković Z. Branches of the anterior communicating artery.

Microsurgical anatomy. Acta Neurochirurgica. 1990;106(1-2):78-85. (Abstract only)

85. Nordon DG, Rodrigues OFJ. Variations in the brain circulation – the circle of Willis. Journal of

Morphological Science. 2012;29(4):243-247.

86. Ogawa A, Suzuki M, Sakurai Y, Yoshimoto T. Vascular anomalies associated with aneurysms of

the anterior communicating artery: microsurgical observations. Journal of Neurosurgery.

1990;72(5):706-709.

87. Tao X, Yu XJ, Bhattarai B, Li TH, Jin H, Wei GW, Ming JS, Ren W, Jiong C. Microsurgical

anatomy of the anterior communicating artery complex in adult Chinese heads. Surgical

Neurology. 2006;65(2):155-161.

88. Türe U, Yaşargil MG, Krisht AF. The arteries of the corpus callosum: a microsurgical anatomic

study. Neurosurgery. 1996;39(6):1075-1084.

89. Makowicz G, Poniatowska R, Lusawa M. Variants of cerebral arteries - anterior circulation. Polish

Journal of Radiology. 2013;78(3):42-47.

90. Laitinen L, Snellman A. Aneurysms of the pericallosal artery. A study of 14 cases verified

angiographically and treated mainly by direct surgical attack. Journal of Neurosurgery.

1960;17:447-458.

91. Izci Y, Agrawal B, Ateş O, Başkaya MK. Superficial vascular anatomy of the medial prefrontal

cortex: an anatomical study. Surgical Neurology. 2009a;72(4):383-388.

92. Canham PB, Finlay HM. Morphometry of medial gaps of human brain artery branches. Stroke.

2004;35(5):1153-1157.

93. Gailloud P, Albayram S, Fasel JH, Beauchamp NJ, Murphy KJ. Angiographic and embryologic

considerations in five cases of middle cerebral artery fenestration. American Journal of



135

94. Teal JS, Rumbaugh CL, Bergeron RT, Segall HD. Angiographic demonstration of fenestrations of

the intradural intracranial arteries. Radiology. 1973a;106(1):123-126.

95. Uchino A, Takase Y, Nomiyama K, Egashira R, Kudo S. Fenestration of the middle cerebral artery

detected by MR angiography. Magnetic Resonance in Medical Sciences. 2006a;5(1):51-55.

96. San-Galli F, Leman C, Kien P, Khazaal J, Phillips SD, Guérin J. Cerebral arterial fenestrations

associated with intracranial saccular aneurysms. Neurosurgery. 1992;30(2):279-283.

97. Hattori T, Kobayashi H. Fenestration of the supraclinoid internal carotid artery associated with

carotid bifurcation aneurysm. Surgical Neurology. 1992;37(4):284-288.

98. Nussbaum ES, Defillo A, Janjua TM, Nussbaum LA. Fenestration of the middle cerebral artery

with an associated ruptured aneurysm. Journal of Clinical Neuroscience. 2009;16(6):845-847.

99. Sun ZK, Li M, Li MH, Li YD, Sun WP, Zhu YQ. Fenestrations accompanied by intracranial

aneurysms assessed with magnetic resonance angiography. Neurology India. 2012;60(1):45.

100. Choudhari KA. Fenestrated anterior cerebral artery. British Journal of Neurosurgery.

2002;16(5):525-529.

101. Matsumura M, Nojiri K. Ruptured anterior communicating artery aneurysms associated with

fenestration of the anterior cerebral artery. Surgical Neurology. 1984;22(4):371-376.

102. Minakawa T, Kawamata M, Hayano M, Kawakami K. Aneurysms associated with fenestrated

anterior cerebral arteries. Report of four cases and review of the literature. Surgical Neurology.

1985;24(3):284-288.

103. Ito J, Washiyama K, Kim CH, Ibuchi Y. Fenestration of the anterior cerebral artery.


104. Yamada T, Inagawa T, Takeda T. Ruptured aneurysm at the anterior cerebral artery fenestration.

Case report. Journal of Neurosurgery. 1982;57(6):826-828.

105. Cooke DL, Stout CE, Kim WT, Kansagra AP, Yu JP, Gu A, Halbach VV. Cerebral arterial

fenestrations. Interventional Neuroradiology. 2014;20(3):261-274.

106. van Rooij SB, Bechan RS, Peluso JP, Sluzewski M, van Rooij WJ. Fenestrations of intracranial

arteries. American Journal of Neuroradiology. 2015;36(6):1167-1170.

107. Bayrak AH, Senturk S, Akay HO, Ozmen CA, Bukte Y, Nazaroglu H. The frequency of intracranial

arterial fenestrations: a study with 64-detector CT-angiography. European Journal of Radiology.

2011;77(3):392-396.


136

108. Vasović L, Trandafilović M, Vlajković S, Jovanović I, Ugrenović S. Anterior Cerebral–Anterior

Communicating Complex in the Postnatal Period: from a Fenestration to the Multiplication of

Arteries. Medicine and Biology. 2014;16(1):1-11.

109. Friedlander RM, Oglivy CS. Aneurysmal subarachnoid hemorrhage in a patient with bilateral A1

fenestrations associated with an azygos anterior cerebral artery. Case report and literature review.

Journal of Neurosurgery. 1996;84(4):681-684.

110. Vucetić RR. Segmental duplication of the fetal anterior cerebral artery. Journal of Anatomy.

1998;192(3):431-443.

111. Ring BA. Middle cerebral artery: anatomical and radio-graphic study. Acta Radiologica.

1962;57:289-300. (Abstract only)

112. Türe U, Yaşargil MG, Al-Mefty O, Yaşargil DC. Arteries of the insula. Journal of Neurosurgery.

2000;92(4):676-687.

113. Idowu OE, Shokunbi MT, Malomo AO, Ogunbiyi JO. Size, course, distribution and anomalies of

the middle cerebral artery in adult Nigerians. East African Medical Journal. 2002;79(4):217-220.

114. Tanriover N, Rhoton AL, Kawashima M, Ulm AJ, Yasuda A. Microsurgical anatomy of the insula

and the sylvian fissure. Journal of Neurosurgery. 2004;100(5):891-922.

115. Isolan GR, de Aguiar PHP, Aires R, Meister CS, Stefani MA. Middle Cerebral Artery

“Pseudotetrafurcation”: Anatomic Report and Review of Middle Cerebral Artery Variations.

Neurosurgery. 2010;20(4):284-287.

116. Grellier P, Roche JL, Duplay J. Radio-anatomical study of the main trunk of the middle cerebral

artery. Neurochirurgie. 1978;24(4):227-233.

117. Teal JS, Rumbaugh CL, Bergeron RT, Segall HD. Anomalies of the middle cerebral artery:

accessory artery, duplication, and early bifurcation. American Journal of Roentgenology, Radium

Therapy, and Nuclear Medicine. 1973b;118(3):567-575.

118. Karazincir S, Ada E, Sarsilmaz A, Yalçin O, Vidinli B, Sahin E. Frequency of vascular variations

and anomalies accompanying intracranial aneurysms. Turkish Journal of Diagnostic and

Interventional Radiology. 2004;10(2):103-109.

119. Ogeng'o JA, Njongo W, Hemed E, Obimbo MM, Gimongo J. Branching pattern of middle cerebral

artery in an African population. Clinical Anatomy. 2011;24(6):692-698.

120. Uchino A, Saito N, Okada Y, Nakajima R. Duplicate origin and fenestration of the middle cerebral

artery on MR angiography. Surgical and Radiologic Anatomy. 2012;34(5):401-404.


137

121. Umansky F, Juarez SM, Dujovny M, Ausman JI, Diaz FG, Gomes F, Mirchandani HG, Ray WJ.

Microsurgical anatomy of the proximal segments of the middle cerebral artery. Journal of


122. Umansky F, Dujovny M, Ausman JI, Diaz FG, Mirchandani HG. Anomalies and variations of the

middle cerebral artery: a microanatomical study. Neurosurgery. 1988;22(6 Pt 1):1023-1027.

123. Meneses MS, Ramina R, Jackowski AP, Pedrozo AA, Pacheco RB, Tsubouchi MH. Middle

cerebral artery revascularization. Anatomical studies and considerations on the anastomosis site.

Arquivos de Neuro-Psiquiatria. 1997;55(1):16-23.

124. Vuillier F, Medeiros E, Moulin T, Cattin F, Bonneville JF, Tatu L. Main anatomical features of the

M1 segment of the middle cerebral artery: a 3D time-of-flight magnetic resonance angiography at

3T study. Surgical and Radiologic Anatomy. 2008;30(6):509-514.

125. Antunes ACM. The microsurgical anatomy of the human middle cerebral artery. Arq Bras

Neurochirurgica. 1985;4:195-208.

126. Umansky F, Gomes FB, Dujovny M, Diaz FG, Ausman JI, Haresh G, Mirchandani HG, Berman

SK. The perforating branches of the middle cerebral artery: A microanatomical study. Journal of


127. Pai SB, Varma RG, Kulkarni RN. Microsurgical anatomy of the middle cerebral artery. Neurology

India. 2005;53(2)186-190.

128. Sadatomo T, Yuki K, Migita K, Imada Y, Kuwabara M, Kurisu K. Differences between middle

cerebral artery bifurcations with normal anatomy and those with aneurysms. Neurosurgical

Review. 2013;36(3):437-445.

129. Anderhuber F, Weiglein A, Pucher RK. Trifurcations of the middle cerebral arteries. Acta

Anatomica. 1990;137(4):342-349.

130. Yamamoto H, Marubayashi T, Soejima T, Matsuoka S, Matsukado Y, Ushio Y. Accessory middle

cerebral artery and duplication of middle cerebral artery- terminology, incidence, vascular etiology,

and developmental significance. Neurologia Medico-chirurgica. 1992;32(5):262-267.

131. Gielecki J, Zurada A, Kozłowska H, Nowak D, Loukas M. Morphometric and volumetric analysis

of the middle cerebral artery in human fetuses. Acta Neurobiologiae Experimentalis.

2009;69(1):129-137.

132. Michotey P, Moscow NP, Salamon G. Anatomy of the cortical branches of the middle cerebral

artery. Radiology of the Skull and Brain. 1974;2:1471-1478.


138

133. Ciszek B, Aleksandrowicz R, Zabek M, Mazurowski W. Classification, topography and

morphometry of the early branches of the middle cerebral artery. Folia Morphologica.

1996;55(4):229-230.

134. Kobari M, Ishihara N, Yunoki K, Togashi O, Sato S. Triplication of the middle cerebral artery

associated with fenestration of the anterior cerebral artery. The Keio Journal of Medicine.

1988;37(4):429-433.

135. Reis CV, Zabramski JM, Safavi-Abbasi S, Hanel RA, Deshmukh P, Preul MC. The accessory

middle cerebral artery: anatomic report. Neurosurgery. 2008;63(1):10-14.

136. Otani N, Nawashiro H, Tsuzuki N, Osada H, Suzuki T, Shima K, Nakai K. A ruptured internal

carotid artery aneurysm located at the origin of the duplicated middle cerebral artery associated

with accessory middle cerebral artery and middle cerebral artery aplasia. Surgical Neurology

International. 2010;16;(1):51.

137. Handa J, Shimizu Y, Matsuda M, Handa H. The accessory middle cerebral artery: report of further

two cases. Clinical Radiology. 1970;21(4):415-416.

138. Uchino M, Kitajima S, Sakata Y, Honda M, Shibata I. Ruptured aneurysm at a duplicated middle

cerebral artery with accessory middle cerebral artery. Acta Neurochirurgica. 2004;146(12):1373-

1374.

139. Kang DH, Park J, Park SH, Hamm IS. Saccular aneurysm at the anterior communicating artery

complex associated with an accessory middle cerebral artery: report of two cases and review of the

literature. Journal of Korean Neurosurgical Society. 2009;46(6):568-571.

140. Komiyama M, Nakajima H, Nishikawa M, Yasui T. Middle Cerebral Artery Variations: Duplicated

and Accessory Arteries. American Journal of Neuroradiology. 1998;19:45-49.

141. Kai Y, Hamada J, Morioka M, Yano S, Kudo M, Kuratsu J. Treatment of unruptured duplicated

middle cerebral artery aneurysm: case report. Surgical Neurology. 2006;65(2):190-193.

142. Tutar NU, Töre HG, Kirbaş I, Tarhan NC, Coşkun M. Various origins of the duplicated middle

cerebral artery. Journal of Neuroimaging. 2008;18(4):448-450.

143. Miyamoto J, Mineura K. Unruptured middle cerebral artery aneurysm associated with a duplicated

middle cerebral artery and a dolichoectasic anterior cerebral artery. Journal of Stroke and

Cerebrovascular Diseases. 2010;19(6):503-506.

144. Chang HY, Kim MS. Middle cerebral artery duplication: classification and clinical implications.

Journal of Korean Neurosurgical Society. 2011;49(2):102-106.


139

145. Crompton MR. The pathology of ruptured middle-cerebral aneurysms with special references to

the differences between the sexes. Lancet. 1962;2(7253):421-425.

146. Milenković Z. Anastomosis between internal carotid artery and anterior cerebral artery with other

anomalies of the circle of Willis in a fetal brain. Journal of Neurosurgery. 1981;55(5):701-703.

147. Kitami K, Kamiyama H, Yasui N. Angiographic analysis of the middle cerebral artery in cerebral

aneurysms-its branching pattern and so-called vascular anomalies. No Shinkei Geka.

1985;13(3):283-290. (Abstract only)

148. Uchino A, Kato A, Takase Y, Kudo S. Middle cerebral artery variations detected by magnetic

resonance angiography. European Journal of Radiology. 2000;10(4):560-563.

149. Uchino A, Sawada A, Takase Y, Kudo S. MR angiography of anomalous branches of the internal

carotid artery. American Journal of Roentgenology. 2003;181(5):1409-1414.

150. Kim MS, Hur JW, Lee JW, Lee HK. Middle cerebral artery anomalies detected by conventional

angiography and magnetic resonance angiography. Journal of Korean Neurosurgical Society.

2005;37:263-267.

151. Lame A, Kaloshi G, Petrela M. Anatomic variants of accessory medial cerebral artery.

Neurosurgery. 2010;66(6):1217.

152. Komiyama M, Nishikawa M, Yasui T. The Accessory Middle Cerebral Artery as a Collateral Blood

Supply. American Journal of Neuroradiology. 1997;18:587-590.

153. Yanaka K, Shirai S, Shibata Y, Nose T. Ruptured Aneurysm at the origin of the Median artery of

the corpus Callosum Associated with accessory middle cerebral artery. Neurologia Medico-

chirurgica. 2000;40:511-514.

154. Kim MS, Lee HK. The angiographic feature and clinical implication of accessory middle cerebral

artery. Journal of Korean Neurosurgical Society. 2009;45(5):289-292.

155. Tacconi L, Johnston FG, Symon L. Accessory middle cerebral artery: case report. Journal of


156. Kahilogullari G, Ugur HC. Accessory Middle Cerebral Artery Originating From Callosomarginal

Artery. Clinical Anatomy. 2006;19:694–695.

157. D'Avila AA, Schneider FL. Microsurgical anatomy of the human basal anterior perforated

substance. Arquivos de Neuro-psiquiatria. 2006;64(2):249-258.

158. Tran-Dinh H. The accessory middle cerebral artery-a variant of the recurrent artery of Heubner (A.

centralis longa)? Acta Anatomica. 1986;126(3):167-171.


140

159. Wakabayashi Y, Hori Y, Kondoh Y, Asano T, Yamada A, Kenai H, Yamashita M, Nagatomi H.

Ruptured anterior cerebral artery aneurysm at the origin of the accessory middle cerebral artery.

Neurologia Medico-chirurgica. 2011;51(9):645-648.

160. Takahashi S, Hoshino F, Uemura K, Takahashi A, Sakamoto K. Accessory middle cerebral artery:

is it a variant form of the recurrent artery of Heubner? American Journal of Neuroradiology.

1989;10(3):563-568.

161. van Rooij S, van Rooij WJ, Sluzewski M, Sprengers ME. Fenestrations of intracranial arteries

detected with 3D rotational angiography. American Journal of Neuroradiology. 2009;30(7):1347-

1350.

162. Uchino A, Kato A, Abe M, Kudo S. Association of cerebral arteriovenous malformation with

cerebral arterial fenestration. European Journal of Radiology. 2001;11(3):493-496.

163. Osborn RE, Kirk G. Cerebral arterial fenestration. Computerized Radiology: Official journal of the

Computerized Tomography Society. 1987;11(3):141-145.

164. Kalia KK, Ross DA, Gutin PH. Multiple arterial fenestrations, multiple aneurysms, and an

arteriovenous malformation in a patient with subarachnoid hemorrhage. Surgical Neurology.

1991;35(1):45-48.

165. Nakamura H, Takada A, Hide T, Ushio Y. Fenestration of the middle cerebral artery associated

with an aneurysm: case report. Neurologia Medico-chirurgica. 1994;34:555-557.

166. Schmieder K, Hardenack M, Harders A. Proximal long fenestration associated with an internal

carotid artery aneurysm. Case illustration. Journal of Neurosurgery. 1997;86(4):733.

167. Yamaguchi S, Ito O, Suzuki S. Coil embolization of a ruptured aneurysm arising from a middle

cerebral artery fenestration-case report. Neurologia Medico-chirurgica. 2010;50(3):213-216.

168. Ito J, Maeda H, Inoue K, Onishi Y. Fenestration of the middle cerebral artery. Neuroradiology.

1977;13(1):37-39.

169. Jeong SK, Kwak HS, Cho YI. Middle cerebral artery fenestration in patients with cerebral

ischemia. Journal of the Neurological Sciences. 2008;15;275:181-184.

170. Perez J, Machado C, Scherle C, Hierro D. Duplicated middle cerebral artery. BMJ Case Reports.

2009;6:2009-2035. doi: 10.1136/bcr.06.2009.2035.

171. Rennert J, Ullrich WO, Schuierer G. A rare case of supraclinoid internal carotid artery (ICA)

fenestration in combination with duplication of the middle cerebral artery (MCA) originating from

the ICA fenestration and an associated aneurysm. Clinical Neuroradiology. 2013;23(2):133-136.


141

172. Imaizumi S, Onuma T, Motohashi O, Kameyama M, Ishii K. Unruptured carotid-duplicated middle

cerebral artery aneurysm: case report. Surgical Neurology. 2002;58(5):322-324.

173. Tabuse M, Wakamoto H, Miyazaki H, Ishiyama N. The usefulness of 3D-CTA for the diagnosis

of a ruptured aneurysm at the origin of the duplicated middle cerebral artery: case report. No

Shinkei Geka. 2002;30(3):327-331. (Abstract only)

174. Miyahara K, Fujitsu K, Ichikawa T, Mukaihara S, Okada T, Kaku S. Unruptured saccular aneurysm

at the origin of the duplicated middle cerebral artery: reports of two cases and review of the

literature. No Shinkei Geka. 2009;37(12):1241-1245. (Abstract only)

175. LaBorde DV, Mason AM, Riley J, Dion JE, Barrow DL. Aneurysm of a duplicate middle cerebral

artery. World Neurosurgery. 2012;77(1):201-204.

176. Elsharkawy A, Ishii K, Niemelä M, Kivisaari R, Lehto H, Hernesniemi J. Management of

aneurysms at the origin of duplicated middle cerebral artery: series of four patients with review of

the literature. World Neurosurgery. 2013;80(6):313-318.

177. Munekata K, Omori H, Kanazawa Y, Miyazaki S, Fukushima H, Kamata K. A case of accessory

middle cerebral artery associated with internal carotid artery aneurysm. No Shinkei Geka.

1979;7(12):1203-1207.

178. Nakamura T, Houkin K, Saitoh H, Abe H. Aneurysm of the anterior communicating artery

associated with accessory middle cerebral artery-case report. Neurologia Medico-chirurgica.

1997;37(10):747-751.

179. Daghigi MH, Tubbs RS, Shoja MM, Shakeri AB, Pourisa M, Salter EG, Oakes WJ. Bilateral

accessory middle cerebral arteries associated with an aneurysm of the anterior circulation. Folia

Morphologica. 2006;65(2):161-163. (Abstract only)

180. Matsuzaki K, Uno M, Fujihara T, Miyamoto T, Yokosuka K, Toi H, Matsubara S, Hirano K.

Ruptured distal accessory anterior cerebral artery aneurysm-case report. Neurologia Medico-

chirurgica. 2011;51(12):839-842.

181. Miyazaki S, Ito K, Ishii S. Aneurysm at the origin of the accessory middle cerebral artery. Surgical

Neurology. 1984;22(3):292-294.

182. Kuwabara S, Naitoh H. Ruptured aneurysm at the origin of the accessory middle cerebral artery:

case report. Neurosurgery. 1990;26(2):320-322. (Abstract only)

183. Han DH, Gwak HS, Chung CK. Aneurysm at the origin of accessory middle cerebral artery

associated with middle cerebral artery aplasia: case report. Surgical Neurology. 1994;42(5):388-

391.


142

184. Sugita S, Yuge T, Miyagi J, Fujimura N, Shigemori M. Giant aneurysm at the origin of the

accessory middle cerebral artery. Surgical Neurology. 1995;44(2):128-130.

185. Georgopoulos CE, Papanikolaou PG, Vlachos KI, Atzemi-Moldow N, Hatzidakis GI. Ruptured

aneurysm at the trunk of the accessory middle cerebral artery. Acta Neurochirurgica.

1999;141(11):1233-1235.

186. Fujiwara K, Saito K, Ebina T. Saccular aneurysm of the accessory middle cerebral artery-case

report. Neurologia medico-chirurgica. 2003;43(1):31-24.

187. Lee IH, Jeon P, Kim KH, Byun HS, Kim HJ, Kim ST, Kim JS. Endovascular treatment of a

ruptured accessory middle cerebral artery aneurysm. Journal of Clinical Neuroscience.

2010;17(3):383-384.

188. Lee CC, Liu ZH, Jung SM, Yang TC. Ruptured aneurysm of the accessory middle cerebral artery

associated with moyamoya disease: a case report. Chang Gung Medical Journal. 2011;34(5):541-

547.

189. Baba M, Shimizu T, Kagawa M, Kitamura K, Kobayashi N. A case of multiple anomalies of

cerebral vessels-fenestration of the middle cerebral artery aneurysm of the anterior communicating

artery and arteriovenous malformation on the frontopolar region. No Shinkei Geka. 1977;5(1):59-

64. (Abstract only)

190. Lazar ML, Bland JE, North RR, Bringewald PR. Middle cerebral artery fenestration. Neurosurgery.

1980;6(3):297-300. (Abstract only)

191. Ueda T, Goya T, Wakisaka S, Kinoshita K. Fenestrations of the middle cerebral artery associated

with aneurysms. American Journal of Neuroradiology. 1984b;5(5):639-640.

192. Fujimura M, Seki H, Sugawara T, Tomichi N, Oku T, Higuchi H. Anomalous internal carotid

artery-anterior cerebral artery anastomosis associated with fenestration and cerebral aneurysm.

Neurologia Medico-chirurgica. 1996;36(4):229-233.

193. Deruty R, Pelissou-Guyotat I, Mottolese C, Bognar L, Laharotte JC, Turjman F. Fenestration of

the middle cerebral artery and aneurysm at the site of the fenestration. Journal of Neurology

Research. 1992;14(5):421-424. (Abstract only)

194. Sim KB, Lee CS, Park JC, Huh JS. Cerebral aneurysm in the long fenestration at the middle portion

of M1 segment. Journal of Korean Neurosurgical Society. 2010;48(5):434-437.

195. Tabuchi S, Yoshioka H. Ruptured aneurysm at the fenestration of the middle cerebral artery

detected by magnetic resonance angiography in a patient with systemic lupus erythematosus and

renal failure: a case report. Journal of Medical Case Reports. 2014;8:30.


143

196. Margolis MT, Newton TH, Hoyt WF. Cortical branches of the posterior cerebral artery. Anatomic-

radiologic correlation. Neuroradiology. 1971;2(3):127-135.

197. Milisavljević M, Marinković S, Marinković Z, Malobabić S. Anatomic basis for surgical approach

to the distal segment of the posterior cerebral artery. Surgical and Radiologic Anatomy.

1988;10(4):259-266. (Abstract only)

198. Yamamoto I, Kageyama N. Microsurgical anatomy of the pineal region. Journal of Neurosurgery.

1980;53(2):205-221.

199. Zeal AA, Rhoton AL. Microsurgical anatomy of the posterior cerebral artery. Journal of


200. Kawashima M, Rhoton AL, Tanriover N, Ulm AJ, Yasuda A, Fujii K. Microsurgical anatomy of

cerebral revascularization. Part II: posterior circulation. Journal of Neurosurgery.

2005b;102(1):132-147.

201. Párraga RG, Ribas GC, Andrade SE, de Oliveira E. Microsurgical anatomy of the posterior cerebral

artery in three-dimensional images. World Neurosurgery. 2011;75(2):233-257.

202. Marinkovic SV, Milisavljevic MM, Lolic-Draganic V, Kovacevic MS. Distribution of the occipital

branches of the posterior cerebral artery. Correlation with occipital lobe infarcts. Stroke.

1987;18:728-732.

203. Gloger S, Gloger A, Vogt H, Kretschmann HJ. Computer-assisted 3D reconstruction of the

terminal branches of the cerebral arteries. III. Posterior cerebral artery and circle of Willis.

Neuroradiology. 1994c;36(4):251-257.

204. Haegelen C, Berton E, Darnault P, Morandi X. A revised classification of the temporal branches

of the posterior cerebral artery. Surgical and Radiologic Anatomy. 2012;34(5):385-391.

205. Ladziński P, Maliszewski M. Variability of the division of the cortical branches of the posterior

cerebral artery. The Anatomical Record. Part A, Discoveries in Molecular, Cellular, and

Evolutionary Biology. 2005;282(1):74-82.

206. Choi CY, Lee CH. A parieto-occipital artery arising from ICA directly and resultant incomplete

PCA. Surgical and Radiologic Anatomy. 2011;33(7):641-643.

207. Buxton PJ, Cook PL. Anomalous origin of the parieto-occipital artery: Case note. Neuroradiology.

1993;35(3):212.

208. Bergquist E. An anomalous posterior cerebral artery. Neuroradiology. 1975;8(4):213-215.

209. Bartosiak P, Borowski S, Golab B. Variation of the origin, the course and branching of posterior

cerebral arteries in man. Folia Morphologica. 1983;42(3):165-173.


144

210. Bisaria KK. Anomalies of the posterior communicating artery and their potential clinical

significance. Journal of neurosurgery. 1984;60(3):572-576.

211. Caruso G, Vincentelli F, Rabehanta P, Giudicelli G, Grisoli F. Anomalies of the P1 segment of the

posterior cerebral artery: Early bifurcation or duplication, fenestration, common trunk with the

superior cerebellar artery. Acta Neurochirurgica. 1991;109:66-71.

212. Gunnal SA, Farooqui MS, Wabale RN. Study of Posterior Cerebral Artery in Human Cadaveric

Brain. Anatomy Research International. 2015;2015:681903. doi: 10.1155/2015/681903.

213. Vlajković S, Vasović L, Trandafilović M, Jovanović I, Ugrenović S, Đorđević G. Fenestrations of

the human posterior cerebral artery. Child's Nervous System. 2015;31(3):381-387.

214. Hacein-Bey L, Muszynski CA, Varelas PN. Saccular aneurysm associated with posterior cerebral

artery fenestration manifesting as a subarachnoid hemorrhage in a child. American Journal of

Neuroradiology. 2002;23(8):1291-1294.

215. Iwashita T, Tanaka Y, Hongo K, Koyama Ji J, Koyama T, Nitta J. Aneurysm originating from the

fenestration of the posterior cerebral artery: case report. Neurosurgery. 2002;50(4):881-884.

216. Pasaoglu L, Hatipoglu HG, Vural M, Ziraman I, Ozcan HN, Koparal S. Persistent primitive

hypoglossal artery and fenestration of posterior cerebral artery: CT and MR angiography.

Neurocirugia (Astur). 2009;20(6):563-566.

217. Pleş H, Loukas M, Iacob N, Andall NR, Miclăuş GD, Tubbs RS, Matusz P. Duplication of the

distal end of the left vertebral artery with fenestration of the right posterior cerebral artery.

Romanian Journal of Morphology and Embryology. 2015;56(2):575-577.

218. Zanini MA, Pereira VM, Jory M, Caldas JG. Giant fusiform aneurysm arising from fenestrated

posterior cerebral artery and basilar tip variation: case report. Neurosurgery. 2009;64(3):E564-565.

219. Gordon-Shaw C. Two Cases of Reduplication of the Arteria Cerebri Posterior. Journal of Anatomy

and Physiology. 1910;44(3):244-248.

220. Binning MJ, Couldwell WT. Fenestration of the oculomotor nerve by a duplicated posterior

cerebral artery and aneurysm. Case report. Journal of Neurosurgery. 2009;111(1):84-86.

221. South Africa. Department of Health. 2003. National Health Act, 2003 (Act No. 61 of 2003).

Government Gazette No. 469:26595 23 July.

222. Tank PW. Grant’s Dissector. Lippincott Williams & Wilkins, A Wolters Kluwer Business; 2009.

223. Marinkovic SV, Milisavljevic MM and Marinkovic ZD. Microanatomy and possible clinical

significance of anastomoses among hypothalamic arteries. Stroke. 1989;20:1341-1352.


145

224. Marinkovic SV, Milisavljevic MM, Kovacevic MS, Stevic ZD. Perforating branches of the middle

cerebral artery. Microanatomy and clinical significance of their intpopulation grouprebral

segments. Stroke. 1985b;16:1022-1029.

225. Delong WB. Anatomy of the Middle Cerebral Artery: The Temporal Branches. Stroke.

1973;4:412-418.

226. Malobabić S, Puskas L, Bogdanović D, Jasović A. Anatomy of the pericallosal pial plexus in man.

Anatomischer Anzeiger. 1989;169(2):125-130.

227. Tanriverdia T, Soualmib L, Oliviera A. The topographic anatomy of the central artery: A

neuronavigational-based study, Annals of Anatomy. 2008;190:146-157.

228. Gomes F, Dujovny M, Umansky F, Ausman JI, Diaz FG, Ray WJ, Mirchandani HG. Microsurgical

anatomy of the recurrent artery of Heubner. Journal of Neurosurgery. 1984;60:130-139.

229. Perlmutter D, Rhoton AL. Microsurgical anatomy of the anterior cerebral-anterior communicating-

recurrent artery complex. Journal of Neurosurgery. 1976;45(3):259-272.

230. El Falougy H, Selmeciova P, Kubikova E, Haviarová Z. The variable origin of the recurrent artery

of Heubner: an anatomical and morphometric study. BioMed Research International. 2013;

doi:10.1155/2013/873434.

231. van der Zwan A, Hillen B, Tulleken CA, Dujovny M. A quantitative investigation of the variability

of the major cerebral arterial territories. Stroke. 1993;24(12):1951-1959.

232. Tarasów E, Abdulwahed SAA, Lewszuk A, Walecki J. Measurements of the middle cerebral artery

in digital subtraction angiography and MR angiography. Medical Science Monitor. 2007;13(1):65-

72.

233. Zurada A, Gielecki J, Tubbs RS, Loukas M, Maksymowicz W, Cohen-Gadol AA, Michalak M,

Chlebiej M, Zurada-Zielińska A. Three-dimensional morphometrical analysis of the M1 segment

of the middle cerebral artery: potential clinical and neurosurgical implications. Clinical Anatomy.

2011;24(1):34-46.

234. Kawashima M, Rhoton AL, Tanriover N, Ulm AJ, Yasuda A, Fujii K. Microsurgical anatomy of

cerebral revascularization. Part I: anterior circulation. Journal of Neurosurgery. 2005a;102(1):116-

131.

235. Krishnamoorthy T, Gupta AK, Bhattacharya RN, Rajesh BJ, Purkayastha S. Anomalous origin of

the callosomarginal artery from the A1 segment with an associated saccular aneurysm. American

Journal of Neuroradiology. 2006;27(10):2075-2077.


146

236. Hong SK. Ruptured proximal anterior cerebral artery (A1) aneurysm located at an anomalous

branching of the fronto-orbital artery-a case report. Journal of Korean Medical Science.

1997;12(6):576-580.

237. Lee ER, Eastwood JD. An unusual variant of the fronto-orbital artery. American Journal of


238. Beevor CE. On the distribution of the different arteries supplying the human brain. Philosophical

Transactions of the Royal Society of London. Series B, Containing Papers of a Biological

Character.1909;1-55. (Abstract only)

239. Wong GK, Wang K, Yu SC, Poon WS. A rare anatomical variant: median anterior cerebral artery

fenestration associated with an azygous infra-optic anterior cerebral artery. Journal of Clinical

Neuroscience. 2010;17(11):1434-1436.

240. Abe S, Fujii K, Nishimura K, Kurokawa K. Azygos anterior cerebral artery aneurysm. Report of

two cases. Neurologia Medico-chirurgica. 1985;25(3):215-218.

241. Kobayashi S, Yuge T, Sugita Y, Kuratomi A, Katayama M, Iryo O, Kobayashi K, Kuboyama M,

Kuramoto S. Azygos anterior cerebral artery aneurysm associated with fenestration of the anterior

cerebral artery. The Kurume Medical Journal. 1986;33(3):149-153.

242. Gibbons K, Hopkins LN, Heros RC. Occlusion of an "accessory" distal anterior cerebral artery

during treatment of anterior communicating artery aneurysms. Report of two cases. Journal of

Neurosurgery. 1991;74(1):133-135.

243. Komiyama M, Yasui T. Accessory middle cerebral artery and moyamoya disease. Journal of

Neurology, Neurosurgery and Psychiatry. 2001;71(1):129-130.

244. Vila Moriente N, Millán Torné M, Capellades Font J, García Sánchez S, Ferrer Avellí X.

Anatomical variations of the middle cerebral artery: duplication and accessory artery. Implications

in the treatment of acute stroke. Revista de Neurolologia. 2004;16-30;38(8):732-735.

245. Mueller DP, Sato Y, Yuh WT. Accessory middle cerebral artery as a source of collateral blood

flow. American Journal of Neuroradiology. 1991;12(6):1223-1224.

246. Hiramatsu Y, Wakita M, Matsuoka H, Kasuya J, Hamada R, Takashima H. Cerebral infarction

associated with accessory middle cerebral arteries: two case reports. Internal Medicine.

2014;53(12):1381-1384.

247. Stabler J. Two cases of accessory middle cerebral artery, including one with an aneurysm at its

origin. The British Journal of Radiology. 1970;43(509):314-318.


147

248. Hori E, Kurosaki K, Matsumura N, Yamatani K, Kusunose M, Kuwayama N, Endo S. Multiple

aneurysms arising from the origin of a duplication of the middle cerebral artery. Journal of Clinical

Neuroscience. 2005;12(7):812-815.

249. Ueda T, Goya T, Kinoshita K, Wakuta Y, Mihara K. Multiple anomalies of cerebral vessels. A

case of multiple aneurysms associated with fenestration of the middle cerebral artery and persistent

primitive trigeminal artery. No Shinkei Geka. 1984a;12(4):531-536. (Abstract only)

250. Gao F, Jiang WJ. Transient ischemic attack associated with stenosis of accessory middle cerebral

artery: a case report. Clinical Neurology and Neurosurgery. 2009;111(7):588-590.

251. van der Zwan A, Hillen B. Review of the variability of the territories of the major cerebral arteries.

Stroke. 1991;22(8):1078-1084.

252. Kaplan HA. The Lateral Perforating Branches of the Anterior and Middle Cerebral Arteries.

Journal of Neurosurgery. 1965;23(3):305-310.


description of the cerebral vasculature in a …

Documents